Oxidative stress alters mitochondrial bioenergetics and modifies pancreatic cell death independently of cyclophilin D, resulting in an apoptosis-to-necrosis shift

DNAJB1-PRKACA fusion protein-regulated LINC00473 promotes tumor growth and alters mitochondrial fitness in fibrolamellar carcinoma

Fibrolamellar carcinoma (FLC) is a rare liver cancer that disproportionately affects adolescents and young adults. Currently, no standard of care is available and there remains a dire need for new therapeutics. Most patients harbor the fusion oncogene DNAJB1-PRKACA (DP fusion), but clinical inhibitors are not yet developed and it is critical to identify downstream mediators of FLC pathogenesis. Here, we identify long noncoding RNA LINC00473 among the most highly upregulated genes in FLC tumors and determine that it is strongly suppressed by RNAi-mediated inhibition of the DP fusion in FLC tumor epithelial cells. We show by loss- and gain-of-function studies that LINC00473 suppresses apoptosis, increases the expression of FLC marker genes, and promotes FLC growth in cell-based and in vivo disease models. Mechanistically, LINC00473 plays an important role in promoting glycolysis and altering mitochondrial activity. Specifically, LINC00473 knockdown leads to increased spare respiratory capacity, which indicates mitochondrial fitness. Overall, we propose that LINC00473 could be a viable target for this devastating disease.

Enhancing stability of liposomes using high molecular weight chitosan to promote antioxidative stress effects and lipid-lowering activity of encapsulated lutein in vivo and in vitro

Lutein is an antioxidant with multiple beneficial functions. However, its therapeutic potential is hampered by its low water solubility and bioavailability. The goal of this study is to compare the stability of lutein-loaded liposomes (Lu-lip) and low (LC)/high molecular weight (HC) chitosan-coated Lu-lip, along with their antioxidant capacity using H2O2-induced HepG2 cells and their lipid-lowering activity using high-fat diet mice. Both LC and HC reduced the lutein degradation rate by 17.5 % and 26.72 % in a challenging environment at pH 6 and T = 4 °C. Compared to LC, the HC coating improved the size- and zeta-potential-stability of Lu-lip at 5 < pH < 7, with the best performance at pH 6. The HC coating prolonged the lutein release profile, increased the cellular uptake of Lu-lip, and reduced the reactive oxygen species (ROS) levels and the H2O2-induced necrotic cell ratios by increasing the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Animal experiments have shown that oral administration of LC and HC coated Lu-lip can significantly reduce body weight levels, total triglycerides (TG), total cholesterol (TC), and non-high-density lipoprotein (n-HDL-C) in high-fat diet mice while significantly increasing the levels of CAT, SOD and GSH-Px in the liver of mice. LC and HC coated Lu-lip can reduce fat accumulation in the liver and epididymal adipose tissue.

Mitochondrial dysfunction in the pathogenesis of acute pancreatitis

The mechanism of cell damage during acute pancreatitis (AP) has not been fully elucidated, and there is still a lack of specific or effective treatments. Increasing evidence has implicated mitochondrial dysfunction as a key event in the pathophysiology of AP. Mitochondrial dysfunction is closely related to calcium (Ca2+) overload, intracellular adenosine triphosphate depletion, mitochondrial permeability transition pore openings, loss of mitochondrial membrane potential, mitophagy damage and inflammatory responses. Mitochondrial dysfunction is an early triggering event in the initiation and development of AP, and this organelle damage may precede the release of inflammatory cytokines, intracellular trypsin activation and vacuole formation of pancreatic acinar cells. This review provides further insight into the role of mitochondria in both physiological and pathophysiological aspects of AP, aiming to improve our understanding of the underlying mechanism which may lead to the development of therapeutic and preventive strategies for AP.

The anti-inflammatory effect of dimethyl trisulfide in experimental acute pancreatitis

Various organosulfur compounds, such as dimethyl trisulfide (DMTS), display anti-inflammatory properties. We aimed to examine the effects of DMTS on acute pancreatitis (AP) and its mechanism of action in both in vivo and in vitro studies. AP was induced in FVB/n mice or Wistar rats by caerulein, ethanol-palmitoleic acid, or L-ornithine-HCl. DMTS treatments were administered subcutaneously. AP severity was assessed by pancreatic histological scoring, pancreatic water content, and myeloperoxidase activity measurements. The behaviour of animals was followed. Pancreatic heat shock protein 72 (HSP72) expression, sulfide, and protein persulfidation were measured. In vitro acinar viability, intracellular Ca2+ concentration, and reactive oxygen species production were determined. DMTS dose-dependently decreased the severity of AP. It declined the pancreatic infiltration of leukocytes and cellular damage in mice. DMTS upregulated the HSP72 expression during AP and elevated serum sulfide and low molecular weight persulfide levels. DMTS exhibited cytoprotection against hydrogen peroxide and AP-inducing agents. It has antioxidant properties and modulates physiological but not pathophysiological Ca2+ signalling. Generally, DMTS ameliorated AP severity and protected pancreatic acinar cells. Our findings indicate that DMTS is a sulfur donor with anti-inflammatory and antioxidant effects, and organosulfur compounds require further investigation into this potentially lethal disease.

Mitochondrial-nuclear communication by FKBP51 shuttling

The HSP90-binding immunophilin FKBP51 is a soluble protein that shows high homology and structural similarity with FKBP52. Both immunophilins are functionally divergent and often show antagonistic actions. They were first described in steroid receptor complexes, their exchange in the complex being the earliest known event in steroid receptor activation upon ligand binding. In addition to steroid-related events, several pleiotropic actions of FKBP51 have emerged during the last years, ranging from cell differentiation and apoptosis to metabolic and psychiatric disorders. On the other hand, mitochondria play vital cellular roles in maintaining energy homeostasis, responding to stress conditions, and affecting cell cycle regulation, calcium signaling, redox homeostasis, and so forth. This is achieved by proteins that are encoded in both the nuclear genome and mitochondrial genes. This implies active nuclear-mitochondrial communication to maintain cell homeostasis. Such communication involves factors that regulate nuclear and mitochondrial gene expression affecting the synthesis and recruitment of mitochondrial and nonmitochondrial proteins, and/or changes in the functional state of the mitochondria itself, which enable mitochondria to recover from stress. FKBP51 has emerged as a serious candidate to participate in these regulatory roles since it has been unexpectedly found in mitochondria showing antiapoptotic effects. Such localization involves the tetratricopeptide repeats domains of the immunophilin and not its intrinsic enzymatic activity of peptidylprolyl-isomerase. Importantly, FKBP51 abandons the mitochondria and accumulates in the nucleus upon cell differentiation or during the onset of stress. Nuclear FKBP51 enhances the enzymatic activity of telomerase. The mitochondrial-nuclear trafficking is reversible, and certain situations such as viral infections promote the opposite trafficking, that is, FKBP51 abandons the nucleus and accumulates in mitochondria. In this article, we review the latest findings related to the mitochondrial-nuclear communication mediated by FKBP51 and speculate about the possible implications of this phenomenon.

Intracellular kynurenine promotes acetaldehyde accumulation, further inducing the apoptosis in soil beneficial fungi Trichoderma guizhouense NJAU4742 under acid stress

In this study, the growth of fungi Trichoderma guizhouense NJAU4742 was significantly inhibited under acid stress, and the genes related to acid stress were identified based on transcriptome analysis. Four genes including tna1, adh2/4, and bna3 were significantly up-regulated. Meanwhile, intracellular hydrogen ions accumulated under acid stress, and ATP synthesis was induced to transport hydrogen ions to maintain hydrogen ion balance. The enhancement of glycolysis pathway was also detected, and a large amount of pyruvic acid from glycolysis was accumulated due to the activity limitation of PDH enzymes. Finally, acetaldehyde accumulated, resulting in the induction of adh2/4. In order to cope with stress caused by acetaldehyde, cells enhanced the synthesis of NAD⁺ by increasing the expression of tna1 and bna3 genes. NAD⁺ effectively improved the antioxidant capacity of cells, but the NAD⁺ supplement pathway mediated by bna3 could also cause the accumulation of kynurenine (KYN), which was an inducer of apoptosis. In addition, KYN had a specific promoting effect on acetaldehyde synthesis by improving the expression of eno2 gene, which led to the extremely high intracellular acetaldehyde in the cell under acidic stress. Our findings provided a route to better understand the response of filamentous fungi under acid stress.

Evidence of impaired mitochondrial cellular bioenergetics in ocular fibroblasts derived from glaucoma patients

Glaucoma is a progressive optic neuropathy characterized by the neurodegeneration of the retinal ganglion cells (RGCs) resulting in irreversible visual impairment and eventual blindness. RGCs are extremely susceptible to mitochondrial compromise due to their marked bioenergetic requirements and morphology. There is increasing interest in therapies targeting mitochondrial health as a method of preventing visual loss in managing glaucoma. The bioenergetic profile of Tenon's ocular fibroblasts from glaucoma patients and controls was investigated using the Seahorse XF24 analyser. Impaired mitochondrial cellular bioenergetics was detected in glaucomatous ocular fibroblasts including basal respiration, maximal respiration and spare capacity. Spare respiratory capacity levels reflect mitochondrial bio-energetic adaptability in response to pathophysiological stress. Basal oxidative stress was elevated in glaucomatous Tenon's ocular fibroblasts and hydrogen peroxide (H₂O₂) induced reactive oxygen species (ROS) simulated the glaucomatous condition in normal Tenon's ocular fibroblasts. This work supports the role of therapeutic interventions to target oxidative stress or provide mitochondrial energetic support in glaucoma.

Transcriptomics and Network Pharmacology Reveal the Protective Effect of Chaiqin Chengqi Decoction on Obesity-Related Alcohol-Induced Acute Pancreatitis via Oxidative Stress and PI3K/Akt Signaling Pathway

Obesity-related acute pancreatitis (AP) is characterized by increasing prevalence worldwide and worse clinical outcomes compared to AP of other etiologies. Chaiqin chengqi decoction (CQCQD), a Chinese herbal formula, has long been used for the clinical management of AP but its therapeutic actions and the underlying mechanisms have not been fully elucidated. This study has investigated the pharmacological mechanisms of CQCQD in a novel mouse model of obesity-related alcohol-induced AP (OA-AP). The mouse OA-AP model was induced by a high-fat diet for 12 weeks and subsequently two intraperitoneal injections of ethanol, CQCQD was administered 2 h after the first injection of ethanol. The severity of OA-AP was assessed and correlated with changes in transcriptomic profiles and network pharmacology in the pancreatic and adipose tissues, and further docking analysis modeled the interactions between compounds of CQCQD and their key targets. The results showed that CQCQD significantly reduced pancreatic necrosis, alleviated systemic inflammation, and decreased the parameters associated with multi-organ dysfunction. Transcriptomics and network pharmacology analysis, as well as further experimental validation, have shown that CQCQD induced Nrf2/HO-1 antioxidant protein response and decreased Akt phosphorylation in the pancreatic and adipose tissues. In vitro, CQCQD protected freshly isolated pancreatic acinar cells from H₂O₂-elicited oxidative stress and necrotic cell death. The docking results of AKT1 and the active compounds related to AKT1 in CQCQD showed high binding affinity. In conclusion, CQCQD ameliorates the severity of OA-AP by activating of the antioxidant protein response and down-regulating of the PI3K/Akt signaling pathway in the pancreas and visceral adipose tissue.

Mitochondrial Inorganic Polyphosphate (polyP) Is a Potent Regulator of Mammalian Bioenergetics in SH-SY5Y Cells: A Proteomics and Metabolomics Study

Inorganic polyphosphate (polyP) is an ancient, ubiquitous, and well-conserved polymer which is present in all the studied organisms. It is formed by individual subunits of orthophosphate which are linked by structurally similar bonds and isoenergetic to those found in ATP. While the metabolism and the physiological roles of polyP have already been described in some organisms, including bacteria and yeast, the exact role of this polymer in mammalian physiology still remains poorly understood. In these organisms, polyP shows a co-localization with mitochondria, and its role as a key regulator of the stress responses, including the maintenance of appropriate bioenergetics, has already been demonstrated by our group and others. Here, using Wild-type (Wt) and MitoPPX (cells enzymatically depleted of mitochondrial polyP) SH-SY5Y cells, we have conducted a comprehensive study of the status of cellular physiology, using proteomics and metabolomics approaches. Our results suggest a clear dysregulation of mitochondrial physiology, especially of bioenergetics, in MitoPPX cells when compared with Wt cells. Moreover, the effects induced by the enzymatic depletion of polyP are similar to those present in the mitochondrial dysfunction that is observed in neurodegenerative disorders and in neuronal aging. Based on our findings, the metabolism of mitochondrial polyP could be a valid and innovative pharmacological target in these conditions.

Teriflunomide Preserves Neuronal Activity and Protects Mitochondria in Brain Slices Exposed to Oxidative Stress

Teriflunomide (TFN) limits relapses in relapsing–remitting multiple sclerosis (RRMS) by reducing lymphocytic proliferation through the inhibition of the mitochondrial enzyme dihydroorotate dehydrogenase (DHODH) and the subsequent modulation of de novo pyrimidine synthesis. Alterations of mitochondrial function as a consequence of oxidative stress have been reported during neuroinflammation. Previously, we showed that TFN prevents alterations of mitochondrial motility caused by oxidative stress in peripheral axons. Here, we aimed to validate TFN effects on mitochondria and neuronal activity in hippocampal brain slices, in which cellular distribution and synaptic circuits are largely preserved. TFN effects on metabolism and neuronal activity were investigated by assessing oxygen partial pressure and local field potential in acute slices. Additionally, we imaged mitochondria in brain slices from the transgenic Thy1-CFP/COX8A)S2Lich/J (mitoCFP) mice using two-photon microscopy. Although TFN could not prevent oxidative stress-related depletion of ATP, it preserved oxygen consumption and neuronal activity in CNS tissue during oxidative stress. Furthermore, TFN prevented mitochondrial shortening and fragmentation of puncta-shaped and network mitochondria during oxidative stress. Regarding motility, TFN accentuated the decrease in mitochondrial displacement and increase in speed observed during oxidative stress. Importantly, these effects were not associated with neuronal viability and did not lead to axonal damage. In conclusion, during conditions of oxidative stress, TFN preserves the functionality of neurons and prevents morphological and motility alterations of mitochondria.

Functional Differences between Proteasome Subtypes

Four proteasome subtypes are commonly present in mammalian tissues: standard proteasomes, which contain the standard catalytic subunits β1, β2 and β5; immunoproteasomes containing the immuno-subunits β1i, β2i and β5i; and two intermediate proteasomes, containing a mix of standard and immuno-subunits. Recent studies revealed the expression of two tissue-specific proteasome subtypes in cortical thymic epithelial cells and in testes: thymoproteasomes and spermatoproteasomes. In this review, we describe the mechanisms that enable the ATP- and ubiquitin-dependent as well as the ATP- and ubiquitin-independent degradation of proteins by the proteasome. We focus on understanding the role of the different proteasome subtypes in maintaining protein homeostasis in normal physiological conditions through the ATP- and ubiquitin-dependent degradation of proteins. Additionally, we discuss the role of each proteasome subtype in the ATP- and ubiquitin-independent degradation of disordered proteins. We also discuss the role of the proteasome in the generation of peptides presented by MHC class I molecules and the implication of having different proteasome subtypes for the peptide repertoire presented at the cell surface. Finally, we discuss the role of the immunoproteasome in immune cells and its modulation as a potential therapy for autoimmune diseases.

Inorganic Polyphosphate, Mitochondria, and Neurodegeneration

With an aging population, the presence of aging-associated pathologies is expected to increase within the next decades. Regrettably, we still do not have any valid pharmacological or non-pharmacological tools to prevent, revert, or cure these pathologies. The absence of therapeutical approaches against aging-associated pathologies can be at least partially explained by the relatively lack of knowledge that we still have regarding the molecular mechanisms underlying them, as well as by the complexity of their etiopathology. In fact, a complex number of changes in the physiological function of the cell has been described in all these aging-associated pathologies, including neurodegenerative disorders. Based on multiple scientific manuscripts produced by us and others, it seems clear that mitochondria are dysfunctional in many of these aging-associated pathologies. For example, mitochondrial dysfunction is an early event in the etiopathology of all the main neurodegenerative disorders, and it could be a trigger of many of the other deleterious changes which are present at the cellular level in these pathologies. While mitochondria are complex organelles and their regulation is still not yet entirely understood, inorganic polyphosphate (polyP) could play a crucial role in the regulation of some mitochondrial processes, which are dysfunctional in neurodegeneration. PolyP is a well-preserved biopolymer; it has been identified in every organism that has been studied. It is constituted by a series of orthophosphates connected by highly energetic phosphoanhydride bonds, comparable to those found in ATP. The literature suggests that the role of polyP in maintaining mitochondrial physiology might be related, at least partially, to its effects as a key regulator of cellular bioenergetics. However, further research needs to be conducted to fully elucidate the molecular mechanisms underlying the effects of polyP in the regulation of mitochondrial physiology in aging-associated pathologies, including neurodegenerative disorders. With a significant lack of therapeutic options for the prevention and/or treatment of neurodegeneration, the search for new pharmacological tools against these conditions has been continuous in past decades, even though very few therapeutic approaches have shown potential in treating these pathologies. Therefore, increasing our knowledge about the molecular mechanisms underlying the effects of polyP in mitochondrial physiology as well as its metabolism could place this polymer as a promising and innovative pharmacological target not only in neurodegeneration, but also in a wide range of aging-associated pathologies and conditions where mitochondrial dysfunction has been described as a crucial component of its etiopathology, such as diabetes, musculoskeletal disorders, and cardiovascular disorders.

Brazilian sunberry (Solanum oocarpum Sendtn): Alkaloid composition and improvement of mitochondrial functionality and insulin secretion of INS-1E cells

Chronic high-glucose levels induce the generation of reactive oxygen species leading to mitochondrial dysfunction, which is one of the pathological triggers in the development of diabetes. This study investigated the alkaloid composition of two fruits of the genus Solanum, fruta-do-lobo (Solanum lycocarpum) and juá-açu (Solanum oocarpum), and their capacity to protect against oxidative damage and defective insulin secretion induced by chronic high-glucose levels. LC-MS and molecular network of fruit crude extracts reveals that juá-açu and fruta-do-lobo contain kukoamines and glycoalkaloids, respectively. Two purification processes were used to enrich those alkaloids. Fruta-do-lobo extract rich in glycoalkaloids showed a strong cytotoxicity effect, however the juá-açu enriched extract was able to protect mitochondrial functionality against glucotoxicity and stimulate insulin secretion even under conditions of hyperglycemia. These results are promising and suggest that juá-açu is a potential source of bioactive compounds for adjuvant/co-adjuvant therapy for diabetes.

Genetic Suppressor Element 1 (GSE1) Promotes the Oncogenic and Recurrent Phenotypes of Castration-Resistant Prostate Cancer by Targeting Tumor-Associated Calcium Signal Transducer 2 (TACSTD2)

BACKGROUND

prostate cancer (PCa) is a principal cause of cancer-related morbidity and mortality. Castration resistance and metastasis are clinical challenges and continue to impede therapeutic success, despite diagnostic and therapeutic advances. There are reports of the oncogenic activity of genetic suppressor element (GSE)1 in breast and gastric cancers; however, its role in therapy resistance, metastasis, and susceptibility to disease recurrence in PCa patients remains unclear.

OBJECTIVE

this study investigated the role of aberrantly expressed GSE1 in the metastasis, therapy resistance, relapse, and poor prognosis of advanced PCa.

METHODS

we used a large cohort of multi-omics data and in vitro, ex vivo, and in vivo assays to investigate the potential effect of altered GSE1 expression on advanced/castration-resistant PCa (CRPC) treatment responses, disease progression, and prognosis.

RESULTS

using a multi-cohort approach, we showed that GSE1 is upregulated in PCa, while tumor-associated calcium signal transducer 2 (TACSTD2) is downregulated. Moreover, the direct, but inverse, correlation interaction between GSE1 and TACSTD2 drives metastatic disease, castration resistance, and disease progression and modulates the clinical and immune statuses of patients with PCa. Patients with GSE1highTACSTD2low expression are more prone to recurrence and disease-specific death than their GSE1lowTACSTD2high counterparts. Interestingly, we found that the GSE1-TACSTD2 expression profile is associated with the therapy responses and clinical outcomes in patients with PCa, especially those with metastatic/recurrent disease. Furthermore, we demonstrate that the shRNA-mediated targeting of GSE1 (shGSE1) significantly inhibits cell proliferation and attenuates cell migration and tumorsphere formation in metastatic PC3 and DU145 cell lines, with an associated suppression of VIM, SNAI2, and BCL2 and the concomitant upregulation of TACSTD2 and BAX. Moreover, shGSE1 enhances sensitivity to the antiandrogens abiraterone and enzalutamide in vitro and in vivo.

CONCLUSION

these data provide preclinical evidence of the oncogenic role of dysregulated GSE1-TACSTD2 signaling and show that the molecular or pharmacological targeting of GSE1 is a workable therapeutic strategy for inhibiting androgen-driven oncogenic signals, re-sensitizing CRPC to treatment, and repressing the metastatic/recurrent phenotypes of patients with PCa.

Pretreatment with chitosan oligosaccharides attenuate experimental severe acute pancreatitis via inhibiting oxidative stress and modulating intestinal homeostasis

Severe acute pancreatitis (SAP) is a severe acute abdominal disease. Recent evidence shows that intestinal homeostasis is essential for the management of acute pancreatitis. Chitosan oligosaccharides (COS) possess antioxidant activity that are effective in treating various inflammatory diseases. In this study we explored the potential therapeutic effects of COS on SAP and underlying mechanisms. Mice were treated with COS (200 mg·kg-1·d-1, po) for 4 weeks, then SAP was induced in the mice by intraperitoneal injection of caerulein. We found that COS administration significantly alleviated the severity of SAP: the serum amylase and lipase levels as well as pancreatic myeloperoxidase activity were significantly reduced. COS administration suppressed the production of proinflammatory cytokines (TNF-α, IL-1β, CXCL2 and MCP1) in the pancreas and ileums. Moreover, COS administration decreased pancreatic inflammatory infiltration and oxidative stress in SAP mice, accompanied by activated Nrf2/HO-1 and inhibited TLR4/NF-κB and MAPK pathways. We further demonstrated that COS administration restored SAP-associated ileal damage and barrier dysfunction. In addition, gut microbiome analyses revealed that the beneficial effect of COS administration was associated with its ability to improve the pancreatitis-associated gut microbiota dysbiosis; in particular, probiotics Akkermansia were markedly increased, while pathogenic bacteria Escherichia-Shigella and Enterococcus were almost eliminated. The study demonstrates that COS administration remarkably attenuates SAP by reducing oxidative stress and restoring intestinal homeostasis, suggesting that COS might be a promising prebiotic agent for the treatment of SAP.

Protective Effects of Necrostatin-1 in Acute Pancreatitis: Partial Involvement of Receptor Interacting Protein Kinase 1

Acute pancreatitis (AP) is a severe and potentially fatal disease caused predominantly by alcohol excess and gallstones, which lacks a specific therapy. The role of Receptor-Interacting Protein Kinase 1 (RIPK1), a key component of programmed necrosis (Necroptosis), is unclear in AP. We assessed the effects of RIPK1 inhibitor Necrostatin-1 (Nec-1) and RIPK1 modification (RIPK1K45A: kinase dead) in bile acid (TLCS-AP), alcoholic (FAEE-AP) and caerulein hyperstimulation (CER-AP) mouse models. Involvement of collateral Nec-1 target indoleamine 2,3-dioxygenase (IDO) was probed with the inhibitor Epacadostat (EPA). Effects of Nec-1 and RIPK1K45A were also compared on pancreatic acinar cell (PAC) fate in vitro and underlying mechanisms explored. Nec-1 markedly ameliorated histological and biochemical changes in all models. However, these were only partially reduced or unchanged in RIPK1K45A mice. Inhibition of IDO with EPA was protective in TLCS-AP. Both Nec-1 and RIPK1K45A modification inhibited TLCS- and FAEE-induced PAC necrosis in vitro. Nec-1 did not affect TLCS-induced Ca2+ entry in PACs, however, it inhibited an associated ROS elevation. The results demonstrate protective actions of Nec-1 in multiple models. However, RIPK1-dependent necroptosis only partially contributed to beneficial effects, and actions on targets such as IDO are likely to be important.

Differential cytotoxicity, ER/oxidative stress, dysregulated AMPKα signaling, and mitochondrial stress by ethanol and its metabolites in human pancreatic acinar cells

BACKGROUND

Alcoholic chronic pancreatitis (ACP) is a serious inflammatory disorder of the exocrine pancreatic gland. A previous study from this laboratory showed that ethanol (EtOH) causes cytotoxicity, dysregulates AMPKα and ER/oxidative stress signaling, and induces inflammatory responses in primary human pancreatic acinar cells (hPACs). Here we examined the differential cytotoxicity of EtOH and its oxidative (acetaldehyde) and nonoxidative (fatty acid ethyl esters; FAEEs) metabolites in hPACs was examined to understand the metabolic basis and mechanism of ACP.

METHODS

We evaluated concentration-dependent cytotoxicity, AMPKα inactivation, ER/oxidative stress, and inflammatory responses in hPACs by incubating them for 6 h with EtOH, acetaldehyde, or FAEEs at clinically relevant concentrations reported in alcoholic subjects using conventional methods. Cellular bioenergetics (mitochondrial stress and a real-time ATP production rate) were determined using Seahorse XFp Extracellular Flux Analyzer in AR42J cells treated with acetaldehyde or FAEEs.

RESULTS

We observed concentration-dependent increases in LDH release, inactivation of AMPKα along with upregulation of ACC1 and FAS (key lipogenic proteins), downregulation of p-LKB1 (an oxidative stress-sensitive upstream kinase regulating AMPKα) and CPT1A (involved in β-oxidation of fatty acids) in hPACs treated with EtOH, acetaldehyde, or FAEEs. Concentration-dependent increases in oxidative stress and ER stress as measured by GRP78, unspliced XBP1, p-eIF2α, and CHOP along with activation of p-JNK1/2, p-ERK1/2, and p-P38MAPK were present in cells treated with EtOH, acetaldehyde, or FAEEs, respectively. Furthermore, a significant decrease was observed in the total ATP production rate with subsequent mitochondrial stress in AR42J cells treated with acetaldehyde and FAEEs.

CONCLUSIONS

EtOH and its metabolites, acetaldehyde and FAEEs, caused cytotoxicity, ER/oxidative and mitochondrial stress, and dysregulated AMPKα signaling, suggesting a key role of EtOH metabolism in the etiopathogenesis of ACP. Because oxidative EtOH metabolism is negligible in the exocrine pancreas, the pathogenesis of ACP could be attributable to the formation of FAEEs and related pancreatic acinar cell injury.

PINK1/PARK2 dependent mitophagy effectively suppresses NLRP3 inflammasome to alleviate acute pancreatitis

BACKGROUND

Acute pancreatitis (AP) is a clinically common acute inflammatory disease in digestive system, leading to systemic inflammatory response syndrome (SIRS) and severe acute pancreatitis (SAP). It was reported that PINK1/PARK2 dependent mitophagy played an important role in various inflammatory diseases. However, its role in AP has not been elucidated. Herein, we explore the effect of mitophagy in the pathogenesis of AP.

METHODS

Firstly, we established cerulein-induced AP group and arginine-induced SAP group based on wild, PINK1^-/- and PARK2^-/- mice. Pancreatic samples were harvested for further investing the mitochondrial dynamics, mitophagy alterations, NLRP3 inflammatory pathway etc. Furthermore, peripheral blood mononuclear cells from SAP patients were collected to examine the expression of mitophagy-related indicators. Additionally, the interrelationship between mitophagy and NLRP3 inflammasome was also explored in AP.

RESULTS

It was confirmed that mitochondria were damaged in both AP and SAP models. The expressions of PINK1, PARK2 and mitochondrial autophagosomes were elevated in wild AP group, which were decreased in SAP group over time. Similarly, the expressions of PINK1 and PAKR2 in peripheral blood mononuclear cells were significantly lower in SAP patients. Besides, in PINK1^-/- and PARK2^-/- mice AP groups, more pronounced inflammatory infiltration, increased apoptotic and necrotic levels and upregulated NLRP3 inflammasome pathway were detected. After injection with MCC950, NLRP3 inflammasome production was notably reduced in PINK1^-/-and PARK2^-/-mice, which effectively alleviated the pancreatic damage and inflammatory cell infiltration.

CONCLUSION

Our study suggested that mitochondrial dysfunction activated PINK1/PARK2-mediated mitophagy in AP, while mitophagy was impaired in SAP. PINK1^-/- and PARK2^-/- mice were more sensitive to onset of SAP and the deficiency of mitophagy could lead to the formation of NLRP3 inflammasome.

Regulated cell death in cisplatin-induced AKI: relevance of myo-inositol metabolism

Regulated cell death (RCD), distinct from accidental cell death, refers to a process of well-controlled programmed cell death with well-defined pathological mechanisms. In the past few decades, various terms for RCDs were coined, and some of them have been implicated in the pathogenesis of various types of acute kidney injury (AKI). Cisplatin is widely used as a chemotherapeutic drug for a broad spectrum of cancers, but its usage was hampered because of being highly nephrotoxic. Cisplatin-induced AKI is commonly seen clinically, and it also serves as a well-established prototypic model for laboratory investigations relevant to acute nephropathy affecting especially the tubular compartment. Literature reports over a period of three decades have indicated that there are multiple types of RCDs, including apoptosis, necroptosis, pyroptosis, ferroptosis, and mitochondrial permeability transition-mediated necrosis, and some of them are pertinent to the pathogenesis of cisplatin-induced AKI. Interestingly, myo-inositol metabolism, a vital biological process that is largely restricted to the kidney, seems to be relevant to the pathogenesis of certain forms of RCDs. A comprehensive understanding of RCDs in cisplatin-induced AKI and their relevance to myo-inositol homeostasis may yield novel therapeutic targets for the amelioration of cisplatin-related nephropathy.

Protective effects of baicalin on caerulein-induced AR42J pancreatic acinar cells by attenuating oxidative stress through miR-136-5p downregulation

Baicalin, the main active component of Scutellaria baicalensis, has antioxidant and anti-apoptotic effects and is used to treat acute pancreatitis; however, its specific mechanism is unclear. This study aims to determine the protective effect and underlying mechanism of baicalin on AR42J pancreatic acinar cell injury. AR42J acinar cells (caerulein, 10 nmol/L) were induced in vitro to establish a cell model for acute pancreatitis. Cell relative survival was measured by thiazolyl blue tetrazolium bromide, and cell apoptosis and death were examined by flow cytometry. The expression levels of superoxide dismutase1 (SOD1), Bax, survivin, Bcl-2, caspase-3, and caspase-7 proteins were analyzed by Western blot, and those of SOD1 mRNA and miR-136-5p were determined by RT-PCR. The activities of GSH, SOD1, ROS, and MDA were also investigated. Compared with those of the caerulein group, the relative survival rate and activity of AR42J pancreatic acinar cells with different baicalin concentrations were significantly increased (p < 0.05), and the supernatant amylase level was markedly decreased (p < 0.05). In addition, the ROS and MDA activities and mir-136-5p expression were significantly decreased, and the GSH activities and SOD1 gene and protein expression levels were markedly increased (p < 0.05). These results suggest that baicalin reduced the caerulein-induced death of AR42J acinar cells and alleviated the caerulein-induced injury in pancreatic acinar cells by inhibiting oxidative stress. The mechanism may be related to the decreased expression of Mir-136-5p and the increased expression of SOD1 gene and protein.

The signaling pathway PI3K/Akt/Nrf2/HO-1 plays a role in the mitochondrial protection promoted by astaxanthin in the SH-SY5Y cells exposed to hydrogen peroxide

The mitochondria are the major source of reactive species in the mammalian cells. Hydrogen peroxide (H₂O₂) is a potent inducer of redox impairment by a mechanism, at least in part, dependent on its ability to impair mitochondrial function. H₂O₂ plays an important role in several pathological conditions, including neurodegeneration and cardiovascular diseases. Astaxanthin (AST) is a xanthophyll that may be found in microalgae, crustaceans, and salmon and exhibits antioxidant and anti-inflammatory effects in different cell types. Even though there is evidence pointing to a role for AST as mitochondrial protectant agent, it was not clearly demonstrated how this xanthophyll attenuates mitochondrial stress. Therefore, we investigated here whether and how AST would be able to prevent the H₂O₂-induced mitochondrial dysfunction in the human neuroblastoma SH-SY5Y cells. We found that AST (20 μM) prevented the H₂O₂-induced loss of mitochondrial membrane potential (MMP) and decrease in the activity of the Complexes I and V. AST pretreatment blocked the mitochondria-related pro-apoptotic effects elicited by H₂O₂. AST upregulated the enzyme heme oxygenase-1 (HO-1) and the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) by a mechanism dependent on the phosphoinositide 3-kinase/Akt (PI3K/Akt) signaling pathway. Inhibition of the PI3K/Akt or of the HO-1 enzyme abolished the AST-induced mitochondrial protection in cells challenged with H₂O₂. Silencing of Nrf2 caused similar effects. Thus, we suggest that AST promotes mitochondrial protection by a mechanism dependent on the PI3K/Akt/Nrf2/HO-1 signaling pathway in SH-SY5Y cells exposed to H₂O₂.

Sleep deprivation induces oxidative stress in the liver and pancreas in young and aging rats

The aging process is characterized by a gradual impairment generally caused by oxidative stress and, more specifically, sleep deprivation, which induces oxidative stress in the brain. The objective of this study was to assess the effect of three types of paradoxical sleep deprivation (PSD): 96 h of PSD (96PSD group); 192 h of PSD (192PSD group); 192 h of PSD followed by a recovery period of 20 days (192PSD + Recovery group) on an oral glucose tolerance test (OGTT), lipid peroxidation (LPO), and superoxide dismutase (SOD) and catalase (CAT) activities in the liver and pancreas of young (3-month-old) and adult (14-month-old) rats. The 96PSD and 192PSD groups of young rats showed lower glucose levels on the OGTT than the control group. In the adult rats, only the 96PSD group had lower glucose levels than the control group. However, the areas under the curve for the young and adult 192 and 192PSD + Recovery groups showed significant differences. Both LPO and SOD increased in the 192PSD and 192PSD + Recovery groups, but CAT decreased in the liver of young rats in the 192PSD group. Regarding the pancreas, LPO and SOD levels increased after 96 h of PSD. In adult animals, CAT decreased in the liver after 96 and 192 h of PSD, while LPO and SOD increased in the pancreas of the 192PSD and PSD + Recovery groups. Differences in the SOD and CAT activities in the liver and SOD activities in the pancreas were also observed between the young and adult rats and maintained across all the PSD groups. In conclusion, PSD induced differential responses that appeared to depend on the duration of the induced condition, the animals’ age, and the tissue analyzed. It was found that adult rats were more susceptible to the effects of PSD than young rats.

The Role of Mitochondria in the Chemoresistance of Pancreatic Cancer Cells

The first-line chemotherapies for patients with unresectable pancreatic cancer (PC) are 5-fluorouracil (5-FU) and gemcitabine therapy. However, due to chemoresistance the prognosis of patients with PC has not been significantly improved. Mitochondria are essential organelles in eukaryotes that evolved from aerobic bacteria. In recent years, many studies have shown that mitochondria play important roles in tumorigenesis and may act as chemotherapeutic targets in PC. In addition, according to recent studies, mitochondria may play important roles in the chemoresistance of PC by affecting apoptosis, metabolism, mtDNA metabolism, and mitochondrial dynamics. Interfering with some of these factors in mitochondria may improve the sensitivity of PC cells to chemotherapeutic agents, such as gemcitabine, making mitochondria promising targets for overcoming chemoresistance in PC.

Mitochondrial dysfunction in nonalcoholic fatty liver disease and alcohol related liver disease

Fatty liver disease constitutes a spectrum of liver diseases which begin with simple steatosis and may progress to advance stages of steatohepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The two main etiologies are-alcohol related fatty liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD). NAFLD is a global health epidemic strongly associated with modern dietary habits and life-style. It is the second most common cause of chronic liver disease in the US after chronic hepatitis C virus (HCV) infection. Approximately 100 million people are affected with this condition in the US alone. Excessive intakes of calories, saturated fat and refined carbohydrates, and sedentary life style have led to explosion of this health epidemic in developing nations as well. ALD is the third most common cause of chronic liver disease in the US. Even though the predominant trigger for onset of steatosis is different in these two conditions, they share common themes in progression from steatosis to the advance stages. Oxidative stress (OS) is considered a very significant contributor to hepatocyte injury in these conditions. Mitochondrial dysfunction contributes to this OS. Role of mitochondrial dysfunction in pathogenesis of fatty liver diseases is emerging but far from completely understood. A better understanding is essential for more effective preventive and therapeutic interventions. Here, we discuss the pathogenesis and therapeutic approaches of NAFLD and ALD from a mitochondrial perspective.

Neuronal Metabolism and Neuroprotection: Neuroprotective Effect of Fingolimod on Menadione-Induced Mitochondrial Damage

Imbalance in the oxidative status in neurons, along with mitochondrial damage, are common characteristics in some neurodegenerative diseases. The maintenance in energy production is crucial to face and recover from oxidative damage, and the preservation of different sources of energy production is essential to preserve neuronal function. Fingolimod phosphate is a drug with neuroprotective and antioxidant actions, used in the treatment of multiple sclerosis. This work was performed in a model of oxidative damage on neuronal cell cultures exposed to menadione in the presence or absence of fingolimod phosphate. We studied the mitochondrial function, antioxidant enzymes, protein nitrosylation, and several pathways related with glucose metabolism and glycolytic and pentose phosphate in neuronal cells cultures. Our results showed that menadione produces a decrease in mitochondrial function, an imbalance in antioxidant enzymes, and an increase in nitrosylated proteins with a decrease in glycolysis and glucose-6-phosphate dehydrogenase. All these effects were counteracted when fingolimod phosphate was present in the incubation media. These effects were mediated, at least in part, by the interaction of this drug with its specific S1P receptors. These actions would make this drug a potential tool in the treatment of neurodegenerative processes, either to slow progression or alleviate symptoms.

Relationship Between Mitochondrial Structure and Bioenergetics in Pseudoxanthoma elasticum Dermal Fibroblasts

Pseudoxanthoma elasticum (PXE) is a genetic disease considered as a paradigm of ectopic mineralization disorders, being characterized by multisystem clinical manifestations due to progressive calcification of skin, eyes, and the cardiovascular system, resembling an age-related phenotype. Although fibroblasts do not express the pathogenic ABCC6 gene, nevertheless these cells are still under investigation because they regulate connective tissue homeostasis, generating the “arena” where cells and extracellular matrix components can promote pathologic calcification and where activation of pro-osteogenic factors can be associated to pathways involving mitochondrial metabolism. The aim of the present study was to integrate structural and bioenergenetic features to deeply investigate mitochondria from control and from PXE fibroblasts cultured in standard conditions and to explore the role of mitochondria in the development of the PXE fibroblasts’ pathologic phenotype. Proteomic, biochemical, and morphological data provide new evidence that in basal culture conditions (1) the protein profile of PXE mitochondria reveals a number of differentially expressed proteins, suggesting changes in redox balance, oxidative phosphorylation, and calcium homeostasis in addition to modified structure and organization, (2) measure of oxygen consumption indicates that the PXE mitochondria have a low ability to cope with a sudden increased need for ATP via oxidative phosphorylation, (3) mitochondrial membranes are highly polarized in PXE fibroblasts, and this condition contributes to increased reactive oxygen species levels, (4) ultrastructural alterations in PXE mitochondria are associated with functional changes, and (5) PXE fibroblasts exhibit a more abundant, branched, and interconnected mitochondrial network compared to control cells, indicating that fusion prevail over fission events. In summary, the present study demonstrates that mitochondria are modified in PXE fibroblasts. Since mitochondria are key players in the development of the aging process, fibroblasts cultured from aged individuals or aged in vitro are more prone to calcify, and in PXE, calcified tissues remind features of premature aging syndromes; it can be hypothesized that mitochondria represent a common link contributing to the development of ectopic calcification in aging and in diseases. Therefore, ameliorating mitochondrial functions and cell metabolism could open new strategies to positively regulate a number of signaling pathways associated to pathologic calcification.

Altered mitochondrial calcium handling and cell death by necroptosis: An emerging paradigm

The classical necroptosis signaling is mediated by death receptors (DRs) that work in synergy with traditional caspase inhibitory signals. Currently, potential therapeutic molecules are in various phases of clinical trials for a spectrum of pathological conditions associated with necroptosis. However, a non-classical model of necroptosis has also emerged over the last decade with a relatively unexplored molecular mechanism. Although in vitro studies and preclinical models have shown its close association with mitochondrial dysfunction (mito-dysfunction), contradictory reports have emerged which complicate its definitiveness. Though impaired mitochondrial calcium ([Ca²⁺]_m) handling is established in necrotic cell death, how this interplay regulates necroptosis is yet to be elucidated. Taking these questions into consideration, we have discussed various molecular aspects of necroptosis with the emerging role of mito-dysfunction. Based on the central role of altered [Ca²⁺]_m handling in mito-dysfunction mediated necroptosis, we have provided a comprehensive molecular insight into this emerging paradigm. Potential reasons for the contradictory findings regarding the role of mito-dysfunction in necroptosis in general and mitochondrial-dependent necroptosis in specific are discussed. We also provide insights into the current understanding of how [Ca²⁺]_m can be a critical determinant in deciding the cell fate under certain pathological conditions, while under others it may be dispensable. Lastly, we have highlighted the key molecular targets which have a direct implication for therapeutic intervention in conditions that are associated with impaired [Ca²⁺]_m handling and cell death by necroptosis.

Fatty acid ethyl ester (FAEE) associated acute pancreatitis: An ex-vivo study using human pancreatic acini

BACKGROUND & AIM

Fatty acid ethyl esters (FAEEs), are produced by non-oxidative alcohol metabolism and can cause acinar cell damage and subsequent acute pancreatitis in rodent models. Even though experimental studies have elucidated the FAEE mediated early intra-acinar events, these mechanisms have not been well studied in humans. In the present study, we evaluate the early intra-acinar events and inflammatory response in human pancreatic acinar tissues and cells in an ex-vivo model.

METHODS

Experiments were conducted using normal human pancreatic tissues exposed to FAEE. Subcellular fractionation was performed on tissue homogenates and trypsin and cathepsin B activities were estimated in these fractions. Acinar cell injury was evaluated by histology and immunohistochemistry. Cytokine release from exposed acinar cells was evaluated by performing Immuno-fluorescence. Serum was collected from patients with AP within the first 72 h of symptom onset for cytokine estimation using FACS.

RESULTS

We observed significant trypsin activation and acinar cell injury in FAEE treated tissue. Cathepsin B was redistributed from lysosomal to zymogen compartment at 30 min of FAEE exposure. IHC results indicated the presence of apoptosis in pancreatic tissue at 1 & 2hrs of FAEE exposure. We also observed a time dependent increase in secretion of cytokines IL-6, IL-8, TNF-α from FAEE treated acinar tissue. There was also a significant elevation in plasma cytokines in patents with alcohol associated AP within 72 h of symptom onset.

CONCLUSION

Our data suggest that alcohol metabolites can cause acute acinar cell damage and subsequent cytokine release which could eventually culminant in SIRS.

Allithiamine Exerts Therapeutic Effects on Sepsis by Modulating Metabolic Flux during Dendritic Cell Activation

Recent studies have highlighted that early enhancement of the glycolytic pathway is a mode of maintaining the pro-inflammatory status of immune cells. Thiamine, a well-known co-activator of pyruvate dehydrogenase complex, a gatekeeping enzyme, shifts energy utilization of glucose from glycolysis to oxidative phosphorylation. Thus, we hypothesized that thiamine may modulate inflammation by alleviating metabolic shifts during immune cell activation. First, using allithiamine, which showed the most potent anti-inflammatory capacity among thiamine derivatives, we confirmed the inhibitory effects of allithiamine on the lipopolysaccharide (LPS)-induced pro-inflammatory cytokine production and maturation process in dendritic cells. We applied the LPS-induced sepsis model to examine whether allithiamine has a protective role in hyper-inflammatory status. We observed that allithiamine attenuated tissue damage and organ dysfunction during endotoxemia, even when the treatment was given after the early cytokine release. We assessed the changes in glucose metabolites during LPS-induced dendritic cell activation and found that allithiamine significantly inhibited glucose-driven citrate accumulation. We then examined the clinical implication of regulating metabolites during sepsis by performing a tail bleeding assay upon allithiamine treatment, which expands its capacity to hamper the coagulation process. Finally, we confirmed that the role of allithiamine in metabolic regulation is critical in exerting anti-inflammatory action by demonstrating its inhibitory effect upon mitochondrial citrate transporter activity. In conclusion, thiamine could be used as an alternative approach for controlling the immune response in patients with sepsis.

Role of mitochondria in pathogenesis of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is global health problem. An estimated 425 million people in the world had diabetes in 2017. It is a major cause of morbidity and mortality worldwide. Although, pathogenesis of T2DM and its complications have been focus of medical research for long, much remains to be learned. A better understanding of molecular pathogenesis is essential for more effective preventive and therapeutic interventions. Role of mitochondria in pathogenesis of metabolic problems such as obesity, metabolic syndrome, and T2DM is the focus of many recent research studies. Mitochondrial dysfunction contributes to the oxidative stress and systemic inflammation leading to insulin resistance (IR). Mitochondria are also essential for pancreatic beta cell insulin secretion. Hence, mitochondria are important players in the pathogenesis of T2DM. In this article, pathogenesis of T2DM is examined from a mitochondrial perspective.

Enniatin B induces dosage-related apoptosis or necrosis in mouse blastocysts leading to deleterious effects on embryo development

The current study has focused on the effects of enniatin B (ENN B, a major mycotoxin produced by Fusarium fungi) on early embryonic development. In in vitro analysis, mouse blastocysts were incubated in medium with ENN B (0-40 μM) or 0.5% DMSO (control group) for 24 hours. In an animal study, blastocysts were collected from mice which were intravenously injected with ENN B (1, 3, 5, and 7mg/kg body weight/day) for 4 days in order to analyze apoptosis and necrosis via Annexin V/PI staining assay; and proliferation using dual differential staining. Exposure to low ENN B concentration (10 μM in vitro and 3 mg/kg/day in vivo) promoted Reactive Oxygen Species (ROS) generation and apoptosis in the Inner Cell Mass (ICM), the mass of cells inside the blastocyst, impairing post-implantation development alone. On the other hand, exposure to a higher ENN B concentration (40 μM in vitro and 7 mg/kg/day in vivo) induced ROS generation and decreased in intracellular ATP which encouraged necrotic processes in both trophectoderm (TE) and ICM of blastocysts leading to impaired implantation and post-implantation development. Moreover, 5 and 7 mg/kg/day ENN B intraperitoneal injection to female mice for 4 days has caused downregulation of CXCL1, IL-1β and IL-8 expressions and increased ROS generation in the liver of newborn mice. Over all, ENN B can induce apoptosis and/or necrosis depending on the treatment dosage in mouse blastocysts. ENN B-induced necrosis in blastocysts may exert long-term harmful effects on next-generation newborns.

Efficiency of the four proteasome subtypes to degrade ubiquitinated or oxidized proteins

The proteasome is responsible for selective degradation of proteins. It exists in mammalian cells under four main subtypes, which differ by the combination of their catalytic subunits: the standard proteasome (β1–β2–β5), the immunoproteasome (β1i–β2i–β5i) and the two intermediate proteasomes (β1–β2–β5i and β1i–β2–β5i). The efficiency of the four proteasome subtypes to degrade ubiquitinated or oxidized proteins remains unclear. Using cells expressing exclusively one proteasome subtype, we observed that ubiquitinated p21 and c-­myc were degraded at similar rates, indicating that the four 26S proteasomes degrade ubiquitinated proteins equally well. Under oxidative stress, we observed a partial dissociation of 26S into 20S proteasomes, which can degrade non-ubiquitinated oxidized proteins. Oxidized calmodulin and hemoglobin were best degraded in vitro by the three β5i-containing 20S proteasomes, while their native forms were not degraded. Circular dichroism analyses indicated that ubiquitin-independent recognition of oxidized proteins by 20S proteasomes was triggered by the disruption of their structure. Accordingly, β5i-containing 20S proteasomes degraded unoxidized naturally disordered protein tau, while 26S proteasomes did not. Our results suggest that the three β5i-containing 20S proteasomes, namely the immunoproteasome and the two intermediate proteasomes, might help cells to eliminate proteins containing disordered domains, including those induced by oxidative stress.

Adiponectin agonist ADP355 ameliorates doxorubicin-induced cardiotoxicity by decreasing cardiomyocyte apoptosis and oxidative stress

Doxorubicin (DOX) is an anthracycline derivative and widely used as an anticancer drug. However, the severe cardiotoxicity of DOX limits its application. ADP355 is an adiponectin-based active peptide with anti-liver fibrosis and atherosclerosis properties. It remains unclear the effects and involved mechanisms of ADP355 in DOX-induced cardiotoxicity. C57BL/6J mice were intraperitoneally injected DOX once a week to induce heart failure while receiving ADP355 treatment daily for 4 weeks. At the end of experiment, blood and heart tissues were collected. We found that ADP355 markedly improved DOX-induced cardiac dysfunction and histopathological damage, and decreased serum creatine kinase, lactate dehydrogenase and hydroxybutyrate dehydrogenase levels. The anti-apoptotic activity of ADP355 was indicated by reduction in TUNEL-positive cells and cleaved caspase-3 expression, along with decreased BCL2-associated X protein/B cell lymphoma 2 (BAX/BCL2) levels in heart tissues. Additionally, ADP355 markedly increased DOX-decreased cell viability by reducing BAX/BCL2, but inhibited reactive oxygen species production in H9c2 cells. Mechanistically, ADP355 attenuated expression of DOX-reduced nuclear factor-erythroid 2-related factor 2 (Nrf2) and superoxide dismutase 2, as well as mRNA levels of Nrf2 downstream targets. Furthermore, ADP355 activated sirtuin 2 and its target genes. In conclusion, we demonstrate that ADP355 alleviates DOX-induced cardiotoxicity by inhibiting myocardial apoptosis and oxidative stress through Nrf2 and sirtuin 2 signaling pathways. These findings suggest that ADP355 can be a promising candidate for the treatment of cardiac dysfunction.

Hypoxia/reoxygenation exacerbates drug-induced cytotoxicity by opening mitochondrial permeability transition pore: Possible application for toxicity screening

Recently, mitochondrial dysfunction is thought of as an important factor leading to a drug-induced liver injury. Our previous reports show that mitochondria-related toxicity, including respiratory chain inhibition (RCI) and reactive oxygen species (ROS) induction, can be detected by the modification of sugar resource substitution and high oxygen condition. However, this in vitro model does not detect mitochondrial permeability transition (MPT)-induced toxicity. Another study with a lipopolysaccharide-pre-administered rodent model showed that ischemia/reperfusion induced ROS, sensitized the susceptibility of MPT pore opening and, finally developed drug-induced liver toxicity. Based on this result, the present study investigated the effect of hypoxia/reoxygenation (H/R) treatment mimicking the ischemia/reperfusion on MPT-dependent toxicity, aiming to construct a system that can evaluate MPT by drugs in hepatocytes. Mitochondrial ROS were enhanced by H/R treatment only in the galactose culture condition. Amiodarone, benzbromarone, flutamide and troglitazone which induced MPT pore opening led to hepatocyte death only in combination with H/R and galactose. Moreover, this alteration was significantly suppressed in hepatocytes lacking cyclophilin D. In conclusion, MPT-induced cytotoxicity can be detected by activating mitochondrial function and H/R. This cell-based assay system could evaluate MPT induced-cytotoxicity by drugs, besides RCI and ROS induction.

Mitochondrial spare respiratory capacity: Mechanisms, regulation, and significance in non-transformed and cancer cells

Mitochondrial metabolism must constantly adapt to stress conditions in order to maintain bioenergetic levels related to cellular functions. This absence of proper adaptation can be seen in a wide array of conditions, including cancer. Metabolic adaptation calls on mitochondrial function and draws on the mitochondrial reserve to meet increasing needs. Among mitochondrial respiratory parameters, the spare respiratory capacity (SRC) represents a particularly robust functional parameter to evaluate mitochondrial reserve. We provide an overview of potential SRC mechanisms and regulation with a focus on its particular significance in cancer cells.

Teriflunomide preserves peripheral nerve mitochondria from oxidative stress-mediated alterations

Mitochondrial dysfunction is a common pathological hallmark in various inflammatory and degenerative diseases of the central nervous system, including multiple sclerosis (MS). We previously showed that oxidative stress alters axonal mitochondria, limiting their transport and inducing conformational changes that lead to axonal damage. Teriflunomide (TFN), an oral immunomodulatory drug approved for the treatment of relapsing forms of MS, reversibly inhibits dihydroorotate dehydrogenase (DHODH). DHODH is crucial for de novo pyrimidine biosynthesis and is the only mitochondrial enzyme in this pathway, thus conferring a link between inflammation, mitochondrial activity and axonal integrity. Here, we investigated how DHODH inhibition may affect mitochondrial behavior in the context of oxidative stress. We employed a model of transected murine spinal roots, previously developed in our laboratory. Using confocal live imaging of axonal mitochondria, we showed that in unmanipulated axons, TFN increased significantly the mitochondria length without altering their transport features. In mitochondria challenged with 50 µM hydrogen peroxide (H₂O₂) to induce oxidative stress, the presence of TFN at 1 µM concentration was able to restore mitochondrial shape, motility, as well as mitochondrial oxidation potential to control levels. No effects were observed at 5 µM TFN, while some shape and motility parameters were restored to control levels at 50 µM TFN. Thus, our data demonstrate an undescribed link between DHODH and mitochondrial dynamics and point to a potential neuroprotective effect of DHODH inhibition in the context of oxidative stress-induced damage of axonal mitochondria.

Activation of AMP-activated protein kinase attenuates ethanol-induced ER/oxidative stress and lipid phenotype in human pancreatic acinar cells

Primary toxicity targets of alcohol and its metabolites in the pancreas are cellular energetics and endoplasmic reticulum (ER). Therefore, the role of AMP-Activated Protein Kinase (AMPKα) in amelioration of ethanol (EtOH)-induced pancreatic acinar cell injury including ER/oxidative stress, inflammatory responses, the formation of fatty acid ethyl esters (FAEEs) and mitochondrial bioenergetics were determined in human pancreatic acinar cells (hPACs) and AR42J cells incubated with/without AMPKα activator [5-aminoimidazole-4-carboxamide ribonucleotide (AICAR)]. EtOH treated hPACs showed concentration and time-dependent increases for FAEEs and inactivation of AMPKα, along with the upregulation of ACC1 and FAS (key lipogenic proteins) and downregulation of CPT1A (involved β-oxidation of fatty acids). These cells also showed significant ER stress as evidenced by the increased expression for GRP78, IRE1α, and PERK/CHOP arm of unfolded protein response promoting apoptosis and activating p-JNK1/2 and p-ERK1/2 with increased secretion of cytokines. AR42J cells treated with EtOH showed increased oxidative stress, impaired mitochondrial biogenesis, and decreased ATP production rate. However, AMPKα activation by AICAR attenuated EtOH-induced ER/oxidative stress, lipogenesis, and inflammatory responses as well as the formation of FAEEs and restored mitochondrial function in hPACs as well as AR42J cells. Therefore, it is likely that EtOH-induced inactivation of AMPKα plays a crucial role in acinar cell injury leading to pancreatitis. Findings from this study also suggest that EtOH-induced inactivation of AMPKα is closely related to ER/oxidative stress and synthesis of FAEEs, as activation of AMPKα by AICAR attenuates formation of FAEEs, ER/oxidative stress and lipogenesis, and improves inflammatory responses and mitochondrial bioenergetics.

Perinuclear mitochondrial clustering, increased ROS levels, and HIF1 are required for the activation of HSF1 by heat stress

The heat shock response (HSR) is a conserved cellular defensive response against stresses such as temperature, oxidative stress and heavy metals. A significant group of players in the HSR is the set of molecular chaperones known as heat shock proteins (HSPs), which assist in the refolding of unfolded proteins and prevent the accumulation of damaged proteins. HSP genes are activated by the HSF1 transcription factor, a master regulator of the HSR pathway. A variety of stressors activate HSF1, but the key molecular players and the processes that directly contribute to HSF1 activation remain unclear. In this study, we show that heat shock induces perinuclear clustering of mitochondria in mammalian cells, and this clustering is essential for activation of the HSR. We also show that this perinuclear clustering of mitochondria results in increased levels of reactive oxygen species in the nucleus, leading to the activation of hypoxia-inducible factor-1α (HIF-1α). To conclude, we provide evidence to suggest that HIF-1α is one of the crucial regulators of HSF1 and that HIF-1α is essential for activation of the HSR during heat shock.

Analysis of Human Natural Killer Cell Metabolism

Natural Killer (NK) cells mediate mainly innate anti-tumor and anti-viral immune responses and respond to a variety of cytokines and other stimuli to promote survival, cellular proliferation, production of cytokines such as interferon gamma (IFNγ) and/or cytotoxicity programs. NK cell activation by cytokine stimulation requires a substantial remodeling of metabolic pathways to support their bioenergetic and biosynthetic requirements. There is a large body of evidence that suggests that impaired NK cell metabolism is associated with a number of chronic diseases including obesity and cancer, which highlights the clinical importance of the availability of a method to determine NK cell metabolism. Here we describe the use of an extracellular flux analyzer, a platform that allows real-time measurements of glycolysis and mitochondrial oxygen consumption, as a tool to monitor changes in the energy metabolism of human NK cells. The method described here also allows for the monitoring of metabolic changes after stimulation of NK cells with cytokines such as IL-15, a system that is currently being investigated in a wide range of clinical trials.

Knockout of the Mitochondrial Calcium Uniporter Strongly Suppresses Stimulus-Metabolism Coupling in Pancreatic Acinar Cells but Does Not Reduce Severity of Experimental Acute Pancreatitis

Acute pancreatitis is a frequent disease that lacks specific drug treatment. Unravelling the molecular mechanisms of acute pancreatitis is essential for the development of new therapeutics. Several inducers of acute pancreatitis trigger sustained Ca²⁺ increases in the cytosol and mitochondria of pancreatic acinar cells. The mitochondrial calcium uniporter (MCU) mediates mitochondrial Ca²⁺ uptake that regulates bioenergetics and plays an important role in cell survival, damage and death. Aberrant Ca²⁺ signaling and mitochondrial damage in pancreatic acinar cells have been implicated in the initiation of acute pancreatitis. The primary aim of this study was to assess the involvement of the MCU in experimental acute pancreatitis. We found that pancreatic acinar cells from MCU^-/- mice display dramatically reduced mitochondrial Ca²⁺ uptake. This is consistent with the drastic changes of stimulus-metabolism coupling, manifested by the reduction of mitochondrial NADH/FAD⁺ responses to cholecystokinin and in the decrease of cholecystokinin-stimulated oxygen consumption. However, in three experimental models of acute pancreatitis (induced by caerulein, taurolithocholic acid 3-sulfate or palmitoleic acid plus ethanol), MCU knockout failed to reduce the biochemical and histological changes characterizing the severity of local and systemic damage. A possible explanation of this surprising finding is the redundancy of damaging mechanisms activated by the inducers of acute pancreatitis.

High-content fluorescence imaging with the metabolic flux assay reveals insights into mitochondrial properties and functions

Metabolic flux technology with the Seahorse bioanalyzer has emerged as a standard technique in cellular metabolism studies, allowing for simultaneous kinetic measurements of respiration and glycolysis. Methods to extend the utility and versatility of the metabolic flux assay would undoubtedly have immediate and wide-reaching impacts. Herein, we describe a platform that couples the metabolic flux assay with high-content fluorescence imaging to simultaneously provide means for normalization of respiration data with cell number; analyze cell cycle distribution; and quantify mitochondrial content, fragmentation state, membrane potential, and mitochondrial reactive oxygen species. Integration of fluorescent dyes directly into the metabolic flux assay generates a more complete data set of mitochondrial features in a single assay. Moreover, application of this integrated strategy revealed insights into mitochondrial function following PGC1a and PRC1 inhibition in pancreatic cancer and demonstrated how the Rho-GTPases impact mitochondrial dynamics in breast cancer.

The mechanism of CaMK2α-MCU-mitochondrial oxidative stress in bupivacaine-induced neurotoxicity

Ca²⁺/calmodulin dependent protein kinase2α (CaMK2α) is a serine/threonine protein kinase in neurons and leads to neuronal injury when it is activated abnormally. Bupivacaine, a local anesthetic commonly used in regional nerve block, could induce neurotoxicity via apoptotic injury. Whether or not CaMK2α is involved in bupivacaine-induced neurotoxicity and it is regulated remains unclear. In this study, bupivacaine was administered for intrathecal injection in C57BL/6 mice for building vivo injury model and was used to culture human neuroblastoma (SH-SY5Y) cells for building vitro injury model. The results showed that bupivacaine induced mitochondrial oxidative stress and neurons apoptotic injury, promoted phosphorylation of CaMK2α and cAMP-response element binding protein (CREB), and elevated mitochondrial Ca²⁺ uniporter (MCU) expression. Furthermore, it induced CaMK2α phosphorylation at Thr286 which phosphorylated CREB at Ser133 and up-regulated MCU transcriptional expression. Inhibition of CaMK2α-MCU signaling with knock-down of CaMK2α and MCU or with inhibitors (KN93 and Ru360) significantly mitigated bupivacaine-induced neurotoxic injury. Over-expression of CaMK2α significantly enhanced above oxidative injury. Activated MCU with agonist (spermine) reversed protective effect of siCaMK2α on bupivacaine-induced mitochondrial oxidative stress. Our data revealed that CaMK2α-MCU-mitochondrial oxidative stress pathway is a major mechanism whereby bupivacaine induces neurotoxicity and inhibition of above signaling could be a therapeutic strategy in the treatment of bupivacaine-induced neurotoxicity.

Pancreatic Acinar Cell Preparation for Oxygen Consumption and Lactate Production Analysis

Mitochondrial dysfunction is a principal feature of acute pancreatitis (AP) although the underlying mechanisms are still unclear. AP precipitants induce Ca²⁺-dependent formation of the mitochondrial permeability transition pore (MPTP) in pancreatic acinar cells (PACs), leading to ATP depletion and necrosis. Evaluations of mitochondrial bioenergetics have mainly been performed in isolated PACs using confocal microscopy, with assessment of mitochondrial membrane potential, NADH/FAD⁺ and ATP levels, coupled with patch-clamp electrophysiology. These studies are technically demanding and time-consuming. Application of Seahorse flux analysis now allows detailed investigations of bioenergetics changes to be performed in cell populations using a multi-well plate-reader format; rates of oxygen consumption (OCR) and extracellular acidification (ECAR) provide important information about cellular respiration and glycolysis, respectively. Parameters such as maximal respiration, ATP-linked capacity and proton leak can be derived from application of a respiratory function "stress" test that involves pharmacological manipulation of the electron transport chain. The use of Seahorse Flux analysis therefore provides a quick, and convenient means to measure detailed cellular bioenergetics and allows results to be coupled with other plate-reader based assays, providing a fuller understanding of the pathophysiological consequences of mitochondrial bioenergetics alterations.

Cross organelle stress response disruption promotes gentamicin-induced proteotoxicity

Gentamicin is a nephrotoxic antibiotic that causes acute kidney injury (AKI) primarily by targeting the proximal tubule epithelial cell. The development of an effective therapy for gentamicin-induced renal cell injury is limited by incomplete mechanistic insight. To address this challenge, we propose that RNAi signal pathway screening could identify a unifying mechanism of gentamicin-induced cell injury and suggest a therapeutic strategy to ameliorate it. Computational analysis of RNAi signal screens in gentamicin-exposed human proximal tubule cells suggested the cross-organelle stress response (CORE), the unfolded protein response (UPR), and cell chaperones as key targets of gentamicin-induced injury. To test this hypothesis, we assessed the effect of gentamicin on the CORE, UPR, and cell chaperone function, and tested the therapeutic efficacy of enhancing cell chaperone content. Early gentamicin exposure disrupted the CORE, evidenced by a rise in the ATP:ADP ratio, mitochondrial-specific H2O2 accumulation, Drp-1-mediated mitochondrial fragmentation, and endoplasmic reticulum-mitochondrial dissociation. CORE disruption preceded measurable increases in whole-cell oxidative stress, misfolded protein content, transcriptional UPR activation, and its untoward downstream effects: CHOP expression, PARP cleavage, and cell death. Geranylgeranylacetone, a therapeutic that increases cell chaperone content, prevented mitochondrial H2O2 accumulation, preserved the CORE, reduced the burden of misfolded proteins and CHOP expression, and significantly improved survival in gentamicin-exposed cells. We identify CORE disruption as an early and remediable cause of gentamicin proteotoxicity that precedes downstream UPR activation and cell death. Preserving the CORE significantly improves renal cell survival likely by reducing organelle-specific proteotoxicity during gentamicin exposure.

Relationship between Optical Redox Status and Reactive Oxygen Species in Cancer Cells

Shifted NAD(H) redox status and enhanced reactive oxygen species (ROS) scavenging systems have been observed in cancers. However, how such redox shift is related to the ROS level in cancer cells is less clear. Based on collecting the intrinsic fluorescence of oxidized flavoproteins (Fp containing flavin adenine dinucleotide) and reduced nicotinamide adenine dinucleotide (NADH), optical redox imaging (ORI) provides a quantitative measure of the mitochondrial redox state by the optical redox ratio, Fp/(NADH+Fp), a surrogate marker of the NAD⁺-coupled redox state NAD⁺/NADH. Our study aims to explore the relationship between NAD(H) redox status and ROS by imaging NADH, Fp, and ROS levels using cultured breast cancer cell models. By manipulating either ROS levels via application of exogenous H₂O₂ or redox status via metabolic perturbation compounds, we found that: (1) oxidation of NAD(H) redox status correlates with ROS levels at lower H₂O₂ concentrations (up to ~700 μM), but not necessarily at higher concentrations; (2) an elevated ROS level diminishes NADH and reduces redox ratio plasticity; (3) either more oxidized or more reduced status can correlate to an increased ROS level; and (4) sometimes, a more oxidized status can correlate to a decreased ROS level depending on cell lines. These observations indicated that cellular NAD(H) redox state and ROS are intricately related but can also change separately. This study can benefit cancer research as both NAD(H) redox status and ROS have been implicated in cancer transformation and progression.

Mitochondrial DNA Copy-Number Variation and Pancreatic Cancer Risk in the Prospective EPIC Cohort

BACKGROUND

Mitochondrial DNA (mtDNA) copy number in peripheral blood has been found to be associated with risk of developing several cancers. However, data on pancreatic ductal adenocarcinoma (PDAC) are very limited.

METHODS

To further our knowledge on this topic, we measured relative mtDNA copy number by a quantitative real-time PCR assay in peripheral leukocyte samples of 476 PDAC cases and 357 controls nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort.

RESULTS

We observed lower mtDNA copy number with advancing age (P = 6.54 × 10-5) and with a high body mass index (BMI) level (P = 0.004) and no association with sex, smoking behavior, and alcohol consumption. We found an association between increased mtDNA copy number and decreased risk of developing PDAC with an odds ratios (OR) of 0.35 [95% confidence interval (CI), 0.16-0.79; P = 0.01] when comparing the fifth quintile with the first using an unconditional logistic regression and an OR of 0.19 (95% CI, 0.07-0.52; P = 0.001) with a conditional analysis. Analyses stratified by BMI showed an association between high mtDNA copy number and decreased risk in the stratum of normal weight, consistent with the main analyses.

CONCLUSIONS

Our results suggest a protective effect of a higher number of mitochondria, measured in peripheral blood leukocytes, on PDAC risk.

IMPACT

Our findings highlight the importance of understanding the mitochondrial biology in pancreatic cancer.

Tetrahydrobenzimidazole TMQ0153 triggers apoptosis, autophagy and necroptosis crosstalk in chronic myeloid leukemia

By comparing imatinib-sensitive and -resistant chronic myeloid leukemia (CML) cell models, we investigated the molecular mechanisms by which tetrahydrobenzimidazole derivative TMQ0153 triggered caspase-dependent apoptosis at low concentrations accompanied by loss of mitochondrial membrane potential (MMP) and increase of cytosolic free Ca²⁺ levels. Interestingly, at higher concentrations, TMQ0153 induced necroptotic cell death with accumulation of ROS, both preventable by N-acetyl-L-cysteine (NAC) pretreatment. At necroptosis-inducing concentrations, we observed increased ROS and decreased ATP and GSH levels, concomitant with protective autophagy induction. Inhibitors such as bafilomycin A1 (baf-A1) and siRNA against beclin 1 abrogated autophagy, sensitized CML cells against TMQ0153 and enhanced necroptotic cell death. Importantly, TMQ153-induced necrosis led to cell surface exposure of calreticulin (CRT) and ERp57 as well as the release of extracellular ATP and high mobility group box (HMGB1) demonstrating the capacity of this compound to release immunogenic cell death (ICD) markers. We validated the anti-cancer potential of TMQ0153 by in vivo inhibition of K562 microtumor formation in zebrafish. Taken together, our findings provide evidence that cellular stress and redox modulation by TMQ0153 concentration-dependently leads to different cell death modalities including controlled necrosis in CML cell models.

Neutrophil Gelatinase-Associated Lipocalin Protects Acinar Cells From Cerulein-Induced Damage During Acute Pancreatitis

OBJECTIVES

Elevated neutrophil gelatinase-associated lipocalin (NGAL) is a promising marker for severe acute pancreatitis (SAP) and multiple organ failure, suggesting systemic and local contributions during pancreatitis. We investigated the role of NGAL locally on acinar cell biology.

METHODS

Western blot, reverse transcriptase-polymerase chain reaction, and immunohistochemistry analysis were performed to analyze the levels of NGAL receptors, apoptotic and regeneration markers, and 4-hydroxynonenal (4HNE) levels, 3-[4,5-Dimethylthiazole-2-yl]-2, 5-diphenyltetrazolium bromide assay, and annexin V/propidium iodide staining were used to evaluate cell viability, and effect on endothelial cells was accessed by endothelial permeability assay.

RESULTS

Cerulein treatment at 20 μM for 12 hours significantly reduced acinar cell viability by 40%, which was rescued by NGAL at 800 and 1600 ng/mL concentrations, observed during mild and SAP, respectively. Mechanistically, NGAL significantly reduced the levels of reactive oxygen species and 4HNE adduct formation in a 24p3R-dependent manner and upregulated the expression of acinar cell regeneration markers, like CDK-2, CDK-4, and C-myc. However, SAP levels of NGAL significantly increased endothelial permeability and downregulated the levels of ZO-1, and cerulein treatment in NGAL knockout mice showed increased levels of 4HNE adducts.

CONCLUSIONS

Neutrophil gelatinase-associated lipocalin rescues intracellular reactive oxygen species during pancreatitis and promotes survival and regeneration of acinar cells.

Altered Bioenergetics of Blood Cell Sub-Populations in Acute Pancreatitis Patients

Acute pancreatitis (AP) is a debilitating, sometimes fatal disease, marked by local injury and systemic inflammation. Mitochondrial dysfunction is a central feature of pancreatic damage in AP, however, its involvement in circulating blood cell subtypes is unknown. This study compared mitochondrial bioenergetics in circulating leukocytes from AP patients and healthy volunteers: 15 patients with mild to severe AP were compared to 10 healthy controls. Monocytes, lymphocytes and neutrophils were isolated using magnetic activated cell sorting and mitochondrial bioenergetics profiles of the cell populations determined using a Seahorse XF24 flux analyser. Rates of oxygen consumption (OCR) and extracellular acidification (ECAR) under conditions of electron transport chain (ETC) inhibition (“stress” test) informed respiratory and glycolytic parameters, respectively. Phorbol ester stimulation was used to trigger the oxidative burst. Basal OCR in all blood cell subtypes was similar in AP patients and controls. However, maximal respiration and spare respiratory capacity of AP patient lymphocytes were decreased, indicating impairment of functional capacity. A diminished oxidative burst occurred in neutrophils from AP patients, compared to controls, whereas this was enhanced in both monocytes and lymphocytes. The data demonstrate important early alterations of bioenergetics in blood cell sub-populations from AP patients, which imply functional alterations linked to clinical disease progression.