Mitochondrial DNA damage and altered membrane potential (ΔΨ) in pancreatic acinar cells induced by reactive oxygen species

Redox signaling in the pancreas in health and disease

This review addresses oxidative stress and redox signaling in the pancreas under healthy physiological conditions as well as in acute pancreatitis, chronic pancreatitis, pancreatic cancer, and diabetes. Physiological redox homeodynamics is maintained mainly by NRF2/KEAP1, NF-κB, protein tyrosine phosphatases, peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α), and normal autophagy. Depletion of reduced glutathione (GSH) in the pancreas is a hallmark of acute pancreatitis and is initially accompanied by disulfide stress, which is characterized by protein cysteinylation without increased glutathione oxidation. A cross talk between oxidative stress, MAPKs, and NF-κB amplifies the inflammatory cascade, with PP2A and PGC1α as key redox regulatory nodes. In acute pancreatitis, nitration of cystathionine-β synthase causes blockade of the transsulfuration pathway leading to increased homocysteine levels, whereas p53 triggers necroptosis in the pancreas through downregulation of sulfiredoxin, PGC1α, and peroxiredoxin 3. Chronic pancreatitis exhibits oxidative distress mediated by NADPH oxidase 1 and/or CYP2E1, which promotes cell death, fibrosis, and inflammation. Oxidative stress cooperates with mutant KRAS to initiate and promote pancreatic adenocarcinoma. Mutant KRAS increases mitochondrial reactive oxygen species (ROS), which trigger acinar-to-ductal metaplasia and progression to pancreatic intraepithelial neoplasia (PanIN). ROS are maintained at a sufficient level to promote cell proliferation, while avoiding cell death or senescence through formation of NADPH and GSH and activation of NRF2, HIF-1/2α, and CREB. Redox signaling also plays a fundamental role in differentiation, proliferation, and insulin secretion of β-cells. However, ROS overproduction promotes β-cell dysfunction and apoptosis in type 1 and type 2 diabetes.

Effects of Zinc Phthalocyanine Photodynamic Therapy on Vital Structures and Processes in Hela Cells

This work presents results on the efficiency of newly designed zinc phthalocyanine-mediated photodynamic therapy of both tumoral and nontumoral cell models using the MTT assay. Further detailed examinations of mechanistic and cell biological effects were focused on the HELA cervical cancer cell model. Here, ROS production, changes in the mitochondrial membrane potential, the determination of genotoxicity, and protein changes determined by capillary chromatography and tandem mass spectrometry with ESI were analyzed. The results showed that, in vitro, 5 Jcm-2 ZnPc PDT caused a significant increase in reactive oxygen species. Still, except for superoxide dismutase, the levels of proteins involved in cell response to oxidative stress did not increase significantly. Furthermore, this therapy damaged mitochondrial membranes, which was proven by a more than 70% voltage-dependent channel protein 1 level decrease and by a 65% mitochondrial membrane potential change 24 h post-therapy. DNA impairment was assessed by an increased level of DNA fragmentation, which might be related to the decreased level of DDB1 (decrease in levels of more than 20% 24 h post-therapy), a protein responsible for maintaining genomic integrity and triggering the DNA repair pathways. Considering these results and the low effective concentration (LC50 = 30 nM), the therapy used is a potentially very promising antitumoral treatment.

The role of mitochondrial damage-associated molecular patterns in acute pancreatitis

Acute pancreatitis (AP) is one of the most common gastrointestinal tract diseases with significant morbidity and mortality. Current treatments remain unspecific and supportive due to the severity and clinical course of AP, which can fluctuate rapidly and unpredictably. Mitochondria, cellular power plant to produce energy, are involved in a variety of physiological or pathological activities in human body. There is a growing evidence indicating that mitochondria damage-associated molecular patterns (mtDAMPs) play an important role in pathogenesis and progression of AP. With the pro-inflammatory properties, released mtDAMPs may damage pancreatic cells by binding with receptors, activating downstream molecules and releasing inflammatory factors. This review focuses on the possible interaction between AP and mtDAMPs, which include cytochrome c (Cyt c), mitochondrial transcription factor A (TFAM), mitochondrial DNA (mtDNA), cardiolipin (CL), adenosine triphosphate (ATP) and succinate, with focus on experimental research and potential therapeutic targets in clinical practice. Preventing or diminishing the release of mtDAMPs or targeting the mtDAMPs receptors might have a role in AP progression.

Obesity-induced oxidative stress and mitochondrial dysfunction negatively affect sperm quality

Obesity is a systemic metabolic disease that can induce male infertility or subfertility through oxidative stress. The aim of this study was to determine how obesity impairs sperm mitochondrial structural integrity and function, and reduces sperm quality in both overweight/obese men and mice on a high-fat diet (HFD). Mice fed the HFD demonstrated higher body weight and increased abdominal fat content than those fed the control diet. Such effects accompanied the decline in antioxidant enzymes, such as glutathione peroxidase (GPX) and catalase and superoxide dismutase (SOD) in testicular and epidydimal tissues. Moreover, malondialdehyde (MDA) content significantly increased in sera. Mature sperm in HFD mice demonstrated higher oxidative stress, including increased mitochondrial reactive oxygen species (ROS) levels and decreased protein expression of GPX1, which may impair mitochondrial structural integrity and reduce mitochondrial membrane potential (MMP) and ATP production. Moreover, cyclic AMPK phosphorylation status increased, whereas sperm motility declined in the HFD mice. Clinical studies demonstrated that being overweight/obese reduced SOD enzyme activity in the seminal plasma and increased ROS in sperm, accompanied by lower MMP and low-quality sperm. Furthermore, ATP content in the sperm was negatively correlated with increases in the BMI of all clinical subjects. In conclusion, our results suggest that excessive fat intake had similar disruptive effects on sperm mitochondrial structure and function, as well as oxidative stress levels in humans and mice, which in turn induced lower sperm motility. This agreement strengthens the notion that fat-induced increases in ROS and impaired mitochondrial function contribute to male subfertility.

JMJD3 Is Required for Acute Pancreatitis and Pancreatitis-Associated Lung Injury

Acute pancreatitis (AP) can be complicated by inflammatory disorders of remote organs, such as lung injury, in which Jumonji domain-containing protein 3 (JMJD3) plays a vital role in proinflammatory responses. Currently, we found that JMJD3 expression was upregulated in the pancreas and lung in an AP male mouse model, which was also confirmed in AP patients. Further experiments revealed that the upregulation of JMJD3 and proinflammatory effects were possibly exerted by mitochondrial DNA (mtDNA) or oxidized-mtDNA from tissue injury caused by AP. The release of mtDNA and oxidized-mtDNA contributed to the infiltration of inflammatory monocytes in lung injury through the stimulator of IFN genes (STING)/TLR9-NF-κB-JMJD3-TNF-α pathway. The inhibition of JMJD3 or utilization of Jmjd3-cKO mice significantly alleviated pulmonary inflammation induced by AP. Blocking mtDNA oxidation or knocking down the TLR9/STING pathway effectively alleviated inflammation. Therefore, inhibition of JMJD3 or STING/TLR9 pathway blockage might be a potential therapeutic strategy to treat AP and the associated lung injury.

The Impact of Oxidative Stress and AKT Pathway on Cancer Cell Functions and Its Application to Natural Products

Oxidative stress and AKT serine-threonine kinase (AKT) are responsible for regulating several cell functions of cancer cells. Several natural products modulate both oxidative stress and AKT for anticancer effects. However, the impact of natural product-modulating oxidative stress and AKT on cell functions lacks systemic understanding. Notably, the contribution of regulating cell functions by AKT downstream effectors is not yet well integrated. This review explores the role of oxidative stress and AKT pathway (AKT/AKT effectors) on ten cell functions, including apoptosis, autophagy, endoplasmic reticulum stress, mitochondrial morphogenesis, ferroptosis, necroptosis, DNA damage response, senescence, migration, and cell-cycle progression. The impact of oxidative stress and AKT are connected to these cell functions through cell function mediators. Moreover, the AKT effectors related to cell functions are integrated. Based on this rationale, natural products with the modulating abilities for oxidative stress and AKT pathway exhibit the potential to regulate these cell functions, but some were rarely reported, particularly for AKT effectors. This review sheds light on understanding the roles of oxidative stress and AKT pathway in regulating cell functions, providing future directions for natural products in cancer treatment.

Genome-Wide Functional Screen for Calcium Transients in Escherichia coli Identifies Increased Membrane Potential Adaptation to Persistent DNA Damage

Calcium plays numerous critical roles in signaling and homeostasis in eukaryotic cells. Far less is known about calcium signaling in bacteria than in eukaryotic cells, and few genes controlling influx and efflux have been identified. Previous work in Escherichia coli showed that calcium influx was induced by voltage depolarization, which was enhanced by mechanical stimulation, which suggested a role in bacterial mechanosensation. To identify proteins and pathways affecting calcium handling in bacteria, we designed a live-cell screen to monitor calcium dynamics in single cells across a genome-wide knockout panel in E. coli The screen measured cells from the Keio collection of knockouts and quantified calcium transients across the population. Overall, we found 143 gene knockouts that decreased levels of calcium transients and 32 gene knockouts that increased levels of transients. Knockouts of proteins involved in energy production and regulation appeared, as expected, as well as knockouts of proteins of a voltage sink, F₁F_o-ATPase. Knockouts of exopolysaccharide and outer membrane synthesis proteins showed reduced transients which refined our model of electrophysiology-mediated mechanosensation. Additionally, knockouts of proteins associated with DNA repair had reduced calcium transients and voltage. However, acute DNA damage did not affect voltage, and the results suggested that only long-term adaptation to DNA damage decreased membrane potential and calcium transients. Our work showed a distinct separation between the acute and long-term DNA damage responses in bacteria, which also has implications for mitochondrial DNA damage in eukaryotes.IMPORTANCE All eukaryotic cells use calcium as a critical signaling molecule. There is tantalizing evidence that bacteria also use calcium for cellular signaling, but much less is known about the molecular actors and physiological roles. To identify genes regulating cytoplasmic calcium in Escherichia coli, we created a single-cell screen for modulators of calcium dynamics. The genes uncovered in this screen helped refine a model for voltage-mediated bacterial mechanosensation. Additionally, we were able to more carefully dissect the mechanisms of adaptation to long-term DNA damage, which has implications for both bacteria and mitochondria in the face of unrepaired DNA.

Pancreatitis in multiple acyl CoA dehydrogenase deficiency: An underdiagnosed complication

BACKGROUND

Multiple acyl-CoA dehydrogenase (MADD) deficiency represents a rare fatty acid oxidation disorder where sporadic reports of pancreatitis already exist. Here, we report three cases of MADD with pancreatic involvement raising questions whether this represents an incidental finding or it is related to the pathophysiology of MADD.

METHODS

We have retrospectively studied the clinical, biochemical and radiologic data of patients with MADD diagnosed in our department over the last 20 years to identify patients with pancreatic involvement.

RESULTS

Three out of 17 patients had pancreatic involvement. All three patients were diagnosed with MADD in the neonatal period (two-third symptomatic-riboflavin nonresponsive, one-third asymptomatic via newborn screening-riboflavin responsive). Age at presentation of pancreatitis ranged from 20 months to 11 years. Presentations included a single episode of acute pancreatitis in the first patient, chronic necrotizing pancreatitis in the second patient, while the third patient was diagnosed with chronic pancreatitis (CP) incidentally through ultrasonography. All patients had inflammation features on either abdominal computed tomography or ultrasound. Pancreatic enzymes were elevated in two patients. Management of pancreatitis was done conservatively while the patient with necrotic CP required subtotal pancreatectomy.

DISCUSSION

Our data suggest that pancreatitis might be more common in patients with MADD than previously reported, requiring a high index of suspicion in patients with acute metabolic decompensation or nonspecific abdominal symptoms. We hypothesize that the underlying mechanism of pancreatitis in MADD is similar to that in mitochondrial disorders, both resulting from disordered energy metabolism and oxidative phosphorylation.

Simvastatin induces autophagic flux to restore cerulein-impaired phagosome-lysosome fusion in acute pancreatitis

BACKGROUND

During pancreatitis, autophagy is activated, but lysosomal degradation of dysfunctional organelles including mitochondria is impaired, resulting in acinar cell death. Retrospective cohort analyses demonstrated an association between simvastatin use and decreased acute pancreatitis incidence.

METHODS

We examined whether simvastatin can protect cell death induced by cerulein and the mechanisms involved during acute pancreatitis. Mice were pretreated with DMSO or simvastatin (20 mg/kg) for 24 h followed by 7 hourly cerulein injections and sacrificed 1 h after last injection to harvest blood and tissue for analysis.

RESULTS

Pancreatic histopathology revealed that simvastatin reduced necrotic cell death, inflammatory cell infiltration and edema. We found that cerulein triggered mitophagy with autophagosome formation in acinar cells. However, autophagosome-lysosome fusion was impaired due to altered levels of LAMP-1, AMPK and ULK-1, resulting in autophagosome accumulation (incomplete autophagy). Simvastatin abrogated these effects by upregulating LAMP-1 and activating AMPK which phosphorylated ULK-1, resulting in increased formation of functional autolysosomes. In contrast, autophagosomes accumulated in control group during pancreatitis. The effects of simvastatin to promote autophagic flux were inhibited by chloroquine. Mitochondria from simvastatin-treated mice were resistant to calcium overload compared to control, suggesting that simvastatin induced mitochondrial quality control to eliminate susceptible mitochondria. Clinical specimens showed a significant increase in cell-free mtDNA in plasma during pancreatitis compared to normal controls. Furthermore, genetic deletion of parkin abrogated the benefits of simvastatin.

CONCLUSION

Our findings reveal the novel role of simvastatin in enhancing autophagic flux to prevent pancreatic cell injury and pancreatitis.

Sinuleptolide inhibits proliferation of oral cancer Ca9-22 cells involving apoptosis, oxidative stress, and DNA damage

OBJECTIVE

Sinuleptolide, a soft corals-derived bioactive norditerpenoid, is a marine natural product with a potent anti-inflammatory effect. We evaluate the potential anti-oral cancer effects of sinuleptolide and investigate the possible mechanisms involved.

DESIGNS

Cell viability, cell cycle, apoptosis, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and DNA damage analyses were performed.

RESULTS

In a cell viability assay, we found that sinuleptolide is dose-responsively antiproliferative against oral gingival cancer Ca9-22 cells but less harmful to normal human gingival fibroblast (HGF-1) cells (P<0.001). In cell cycle analysis, sinuleptolide induced subG1 accumulation at a higher dose and led to G2/M arrest of Ca9-22 cells (P<0.005). Apoptosis was significantly increased in sinuleptolide-treated Ca9-22 cells based on annexin V and poly(ADP-ribose) polymerase (PARP) expressions (P<0.05-0.0001). Based on flow cytometer analysis, sinuleptolide also induced the generation of ROS and decreased MMP in a dose-responsive manner (P<0.05-0.0001). DNA damage increased dose-responsively after sinuleptolide treatments (P < 0.001) based on comet and γH2AX assays.

CONCLUSION

Sinuleptolide can induce an antiproliferation of oral cancer Ca9-22 cells involving apoptosis, oxidative stress and DNA damage, suggesting that sinuleptolide represents a potential chemotherapeutic drug for oral cancer treatment.

UV-B exposure reduces locomotor performance by impairing muscle function but not mitochondrial ATP production

Ultraviolet B radiation (UV-B) can reduce swimming performance by increasing reactive oxygen species (ROS) formation. High concentrations of ROS can damage mitochondria, resulting in reduced ATP production. ROS can also damage muscle proteins, thereby leading to impaired muscle contractile function. We have shown previously that UV-B exposure reduces locomotor performance in mosquitofish (Gambusia holbrooki) without affecting metabolic scope. Our aim was therefore to test whether UV-B influences swimming performance of mosquitofish by ROS-induced damage to muscle proteins without affecting mitochondrial function. In a fully factorial design, we exposed mosquitofish to UV-B and no-UV-B controls in combination with exposure to N-acetylcysteine (NAC) plus no-NAC controls. We used NAC, a precursor of glutathione, as an antioxidant to test whether any effects of UV-B on swimming performance were at least partly due to UV-B-induced ROS. UV-B significantly reduced critical sustained swimming performance and tail beat frequencies, and it increased ROS-induced damage (protein carbonyl concentrations and lipid peroxidation) in muscle. However, UV-B did not affect the activity of sarco-endoplasmic reticulum ATPase (SERCA), an enzyme associated with muscle calcium cycling and muscle relaxation. UV-B did not affect ADP phosphorylation (state 3) rates of mitochondrial respiration, and it did not alter the amount of ATP produced per atom of oxygen consumed (P:O ratio). However, UV-B reduced the mitochondrial respiratory control ratio. Under UV-B exposure, fish treated with NAC showed greater swimming performance and tail beat frequencies, higher glutathione concentrations, and lower protein carbonyl concentrations and lipid peroxidation than untreated fish. Tail beat amplitude was not affected by any treatment. Our results showed, firstly, that the effects of UV-B on locomotor performance were mediated by ROS and, secondly, that reduced swimming performance was not caused by impaired mitochondrial ATP production. Instead, reduced tail beat frequencies indicate that muscle of UV-B exposed fish were slower, which was likely to have been caused by slower contraction rates, because SERCA activities remained unaffected.

Cardioprotective HIF-1α-frataxin signaling against ischemia-reperfusion injury

Previous studies have demonstrated the protective signaling of hypoxia-inducible factor (HIF)-1 α against ischemia-reperfusion (I/R) injury in the heart. In the present study, we provide further evidence for a cardioprotective mechanism by HIF-1α against I/R injury exerted via the mitochondrial protein frataxin, which regulates mitochondrial Fe-S cluster formation. Disruption of frataxin has been found to induce mitochondrial iron overload and subsequent ROS production. We observed that frataxin expression was elevated in mice hearts subjected to I/R injury, and this response was blunted in cardiomyocyte-specific HIF-1α knockout (KO) mice. Furthermore, these HIF-1α KO mice sustained extensive cardiac damage from I/R injury compared with control mice. Similarly, reduction of HIF-1α by RNA inhibition resulted in an attenuation of frataxin expression in response to hypoxia in H9C2 cardiomyocytes. Therefore, we postulated that HIF-1α transcriptionally regulates frataxin expression in response to hypoxia and offers a cardioprotective mechanism against ischemic injury. Our promoter activity and chromatin immunoprecipitation assays confirmed the presence of a functional hypoxia response element in the frataxin promoter. Our data also suggest that increased frataxin mitigated mitochondrial iron overload and subsequent ROS production, thus preserving mitochondrial membrane integrity and viability of cardiomyocytes. We postulate that frataxin may exert its beneficial effects by acting as an iron storage protein under hypoxia and subsequently facilitates the maintenance of mitochondrial membrane potential and promotes cell survival. The findings from our study revealed that HIF-1α-frataxin signaling promotes a protective mechanism against hypoxic/ischemic stress.

Mitochondrial Malfunctioning, Proteasome Arrest and Apoptosis in Cancer Cells by Focused Intracellular Generation of Oxygen Radicals

Photofrin/photodynamic therapy (PDT) at sub-lethal doses induced a transient stall in proteasome activity in surviving A549 (p53^+/+) and H1299 (p53^−/−) cells as indicated by the time-dependent decline/recovery of chymotrypsin-like activity. Indeed, within 3 h of incubation, Photofrin invaded the cytoplasm and localized preferentially within the mitochondria. Its light activation determined a decrease in mitochondrial membrane potential and a reversible arrest in proteasomal activity. A similar result is obtained by treating cells with Antimycin and Rotenone, indicating, as a common denominator of this effect, the ATP decrease. Both inhibitors, however, were more toxic to cells as the recovery of proteasomal activity was incomplete. We evaluated whether combining PDT (which is a treatment for killing tumor cells, per se, and inducing proteasome arrest in the surviving ones) with Bortezomib doses capable of sustaining the stall would protract the arrest with sufficient time to induce apoptosis in remaining cells. The evaluation of the mitochondrial membrane depolarization, residual proteasome and mitochondrial enzymatic activities, colony-forming capabilities, and changes in protein expression profiles in A549 and H1299 cells under a combined therapeutic regimen gave results consistent with our hypothesis.

Comparative Phytochemical Analysis of Essential Oils from Different Biological Parts of Artemisia herba alba and Their Cytotoxic Effect on Cancer Cells

PURPOSE

Carrying out the chemical composition and antiproliferative effects against cancer cells from different biological parts of Artemisia herba alba.

METHODS

Essential oils were studied by gas chromatography coupled to mass spectrometry (GC-MS) and their antitumoral activity was tested against P815 mastocytoma and BSR kidney carcinoma cell lines; also, in order to evaluate the effect on normal human cells, oils were tested against peripheral blood mononuclear cells PBMCs.

RESULTS

Essential oils from leaves and aerial parts (mixture of capitulum and leaves) were mainly composed by oxygenated sesquiterpenes 39.89% and 46.15% respectively; capitulum oil contained essentially monoterpenes (22.86%) and monocyclic monoterpenes (21.48%); esters constituted the major fraction (62.8%) of stem oil. Essential oils of different biological parts studied demonstrated a differential antiproliferative activity against P815 and BSR cancer cells; P815 cells are the most sensitive to the cytotoxic effect. Leaves and capitulum essential oils are more active than aerial parts. Interestingly, no cytotoxic effect of these essential oils was observed on peripheral blood mononuclear cells.

CONCLUSION

Our results showed that the chemical composition variability of essential oils depends on the nature of botanical parts of Artemisia herba alba. Furthermore, we have demonstrated that the differential cytotoxic effect depends not only on the essential oils concentration, but also on the target cells and the botanical parts of essential oils used.

Antiproliferative effects of methanolic extracts of Cryptocarya concinna Hance roots on oral cancer Ca9-22 and CAL 27 cell lines involving apoptosis, ROS induction, and mitochondrial depolarization

Cryptocarya-derived natural products were reported to have several biological effects such as the antiproliferation of some cancers. The possible antioral cancer effect of Cryptocarya-derived substances was little addressed as yet. In this study, we firstly used the methanolic extracts of C. concinna Hance roots (MECCrt) to evaluate its potential function in antioral cancer bioactivity. We found that MECCrt significantly reduced cell viability of two oral cancer Ca9-22 and CAL 27 cell lines in dose-responsive manners (P < 0.01). The percentages of sub-G1 phase and annexin V-positive of MECCrt-treated Ca9-22 and CAL 27 cell lines significantly accumulated (P < 0.01) in a dose-responsive manner as evidenced by flow cytometry. These apoptotic effects were associated with the findings that intracellular ROS generation was induced in MECCrt-treated Ca9-22 and CAL 27 cell lines in dose-responsive and time-dependent manners (P < 0.01). In a dose-responsive manner, MECCrt also significantly reduced the mitochondrial membrane potential in these two cell lines (P < 0.01–0.05). In conclusion, we demonstrated that MECCrt may have antiproliferative potential against oral cancer cells involving apoptosis, ROS generation, and mitochondria membrane depolarization.

Antiproliferative effects of goniothalamin on Ca9-22 oral cancer cells through apoptosis, DNA damage and ROS induction

Goniothalamin (GTN), a plant bioactive styryl-lactone, is a natural product with potent anti-tumorigenesis effects for several types of cancer. Nonetheless, the anticancer effect of GTN has not been examined in oral cancer. The present study was designed to evaluate its potential anticancer effects in an oral squamous cell carcinoma (OSCC) model and to determine the possible mechanisms with respect to apoptosis, DNA damage, reactive oxygen species (ROS) induction, and mitochondrial membrane potential. Our data demonstrated that cell proliferation was significantly inhibited by GTN in Ca9-22 OSCC cancer cells in concentration- and time-dependent manners (p<0.05). For cell cycle and apoptotic effects of GTN-treated Ca9-22 cancer cells, the sub-G1 population and annexin V-intensity significantly increased in a concentration-dependent manner (p<0.001). For the analysis of DNA double strand breaks, γH2AX intensity significantly increased in GTN-treated Ca9-22 cancer cells in concentration-response relationship (p<0.05). Moreover, GTN significantly induced intracellular ROS levels in Ca9-22 cancer cells in a concentration- and time-dependent manner (p<0.05). For membrane depolarization of mitochondria, the DiOC(2)(3) (3,3'-diethyloxacarbocyanine iodide) intensity of GTN-treated Ca9-22 cancer cells was significantly decreased in concentration- and time-dependent relationships (p<0.001). Taken together, these results suggest that the anticancer effect of GTN against oral cancer cells is valid and GTN-induced growth inhibition and apoptosis influence the downstream cascade including ROS induction, DNA damage, and mitochondria membrane depolarization. Therefore, GTN has potential as a chemotherapeutic agent against oral cancer.

Involvement of P2Y receptors in the protective effect of ATP towards the cell damage in HaCaT cells exposed to H₂O₂

It has recently been reported that activation of P2Y(1) receptor, one of the purine receptors, by extracellular nucleotides induces cytoprotection against oxidative stress. In this study, we examined the protective effect of ATP on the cell damage in human epidermal keratinocyte HaCaT cells exposed to H(2)O(2) via the P2Y receptor-mediated induction of intracellular antioxidants. The cells were damaged by exposure to H(2)O(2) in a dose- and time-dependent manner. The damage induced by 7.5 mM H(2)O(2) was blocked by pretreatment of the cells with ATP (1-10 µM). The protective effect of ATP was significantly reduced by P2Y receptor antagonists. Exogenously added ATP induced various intracellular antioxidants, including thiol-containing proteins, Cu/Zn superoxide dismutase (SOD) and thioredoxin-1, in HaCaT cells. In conclusion, it was found that ATP protected the cells from the H(2)O(2)-induced cell damages via the P2Y receptor-mediated induction of intracellular antioxidants.

Redox signaling and histone acetylation in acute pancreatitis

Histone acetylation via CBP/p300 coordinates the expression of proinflammatory cytokines in the activation phase of inflammation, particularly through mitogen-activated protein kinases (MAPKs), nuclear factor-κB (NF-κB), and signal transducers and activators of transcription (STAT) pathways. In contrast, histone deacetylases (HDACs) and protein phosphatases are mainly involved in the attenuation phase of inflammation. The role of reactive oxygen species (ROS) in the inflammatory cascade is much more important than expected. Mitochondrial ROS act as signal-transducing molecules that trigger proinflammatory cytokine production via inflammasome-independent and inflammasome-dependent pathways. The major source of ROS in acute inflammation seems to be NADPH oxidases, whereas NF-κB, protein phosphatases, and HDACs are the major targets of ROS and redox signaling in this process. There is a cross-talk between oxidative stress and proinflammatory cytokines through serine/threonine protein phosphatases, tyrosine protein phosphatases, and MAPKs that greatly contributes to amplification of the uncontrolled inflammatory cascade and tissue injury in acute pancreatitis. Chromatin remodeling during induction of proinflammatory genes would depend primarily on phosphorylation of transcription factors and their binding to gene promoters together with recruitment of histone acetyltransferases. PP2A should be considered a key modulator of the inflammatory cascade in acute pancreatitis through the ERK/NF-κB pathway and histone acetylation.

The Renin-angiotensin system and reactive oxygen species: implications in pancreatitis

SIGNIFICANCE

The renin-angiotensin system (RAS) is a circulating hormonal system involved in the regulation of blood pressure and circulating fluid electrolytes. Recent findings have revealed that locally generated angiotensin (Ang) II plays a pivotal role in normal physiology as well as pathophysiology in various tissues and organs, including the pancreas. This review article summarizes current progress that has been made in elucidating the putative roles of Ang II in both acute and chronic pancreatitis.

RECENT ADVANCES

A convergence of evidence suggests that the underlying mechanism may involve reactive oxygen species (ROS)-generating systems, such as nicotinamide adenine dinucleotide phosphate oxidase, and subsequent elevation of proinflammatory and profibrogenic gene expression as well as protein activity. More importantly, Ang II-induced ROS interacts with other ROS-generating systems to positively feed-forward the ROS-induced signaling.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Advances in basic research indicate that RAS blockers may provide potential therapeutic role for the management of pancreatic inflammation and, more importantly, pancreatitis-associated complications. Genetic alterations resulting from a malfunction in the epigenetic control of pancreatic RAS could be a causative factor in the development of pancreatitis.

Nelfinavir/ritonavir reduces acinar injury but not inflammation during mouse caerulein pancreatitis

There is no clinical treatment that reduces acinar injury during pancreatitis. Human immunodeficiency virus (HIV) protease inhibitors (PI), including nelfinavir (NFV) and ritonavir (RTV), may reduce the rate of pancreatitis in HIV-infected patients. Since permeability transition pore (PTPC)-mediated mitochondrial dysfunction occurs during pancreatitis, and we have shown that PI prevents PTPC opening, we studied its effects in a model of pancreatitis. The effect of NFV plus RTV (NFV/RTV) or vehicle on caerulein-induced pancreatitis in mice was compared by measuring changes in mitochondrial membrane potential in vitro and cytochrome c leakage in vivo. Histological and inflammatory makers were also compared. NFV/RTV improved DiOC6 retention in acini exposed to caerulein in vitro. In vivo NFV prevented cytosolic leakage of cytochrome c and reduced pancreatic acinar injury, active caspase-3 staining, TUNEL-positive acinar cells, and serum amylase (P < 0.05). Conversely, trypsin activity, serum cytokine levels, and pancreatic and lung inflammation were unaffected. NFV/RTV reduces pancreatic injury and acinar cell death in experimental mouse caerulein-induced pancreatitis but does not impact inflammation.

Role of oxidative stress in pancreatic inflammation

Reactive oxygen and reactive nitrogen species (ROS/RNS) have been implicated in the pathogenesis of acute and chronic pancreatitis. Clinical and basic science studies have indicated that ROS/RNS formation processes are intimately linked to the development of the inflammatory disorders. The detrimental effects of highly reactive ROS/RNS are mediated by their direct actions on biomolecules (lipids, proteins, and nucleic acids) and activation of proinflammatory signal cascades, which subsequently lead to activation of immune responses. The present article summarizes the possible sources of ROS/RNS formation and the detailed signaling cascades implicated in the pathogenesis of pancreatic inflammation, as observed in acute and chronic pancreatitis. A therapeutic ROS/RNS-scavenging strategy has been advocated for decades; however, clinical studies examining such approaches have been inconsistent in their results. Emerging evidence indicates that pancreatitis-inducing ROS/RNS generation may be attenuated by targeting ROS/RNS-generating enzymes and upstream mediators.

Recurrent pancreatitis in mitochondrial cytopathy

Diabetes mellitus and exocrine insufficiency are the commonest pancreatic manifestations of mitochondrial diseases. In contrast, pancreatitis has rarely been described in mitochondrial syndromes. We report on a patient with Kearns-Sayre syndrome and recurrent episodes of acute pancreatitis for which no explanation could be found other than the associated mitochondrial dysfunction. Interestingly, pharmacological disruption of mitochondrial metabolism in various models as well as in patients can cause pancreatitis, further supporting this association. A diagnosis of pancreatitis should be considered in any patients with mitochondrial disease and recurrent abdominal pain.

Free radicals and the pancreatic acinar cells: role in physiology and pathology

Reactive oxygen and nitrogen species (ROS and RNS) play an important role in signal transduction and cell injury processes. Nitric oxide synthase (NOS)-the key enzyme producing nitric oxide (NO)-is found in neuronal structures, vascular endothelium and, possibly, in acinar and ductal epithelial cells in the pancreas. NO is known to regulate cell homeostasis, and its effects on the acinar cells are reviewed here. ROS are implicated in the early events within the acinar cells, leading to the development of acute pancreatitis. The available data on ROS/RNS involvement in the apoptotic and necrotic death of pancreatic acinar cells will be discussed.

Vitamin D sensitizes breast cancer cells to the action of H2O2: mitochondria as a convergence point in the death pathway

Calcitriol, the hormonal form of vitamin D3, sensitizes breast cancer cells to reactive oxygen species (ROS)-dependent cytotoxicity induced by various anticancer modalities. This effect could be due to increased generation of ROS and/ or to increased sensitivity of the target cells to ROS. This work examined the effect of calcitriol on the damage inflicted on breast cancer cells by the direct action of ROS represented by H2O2. Treatment of MCF-7 cells with H2O2 resulted in activation of caspase 7 as well as induction of caspase-independent cell death. Both were enhanced by 48-72 h of pretreatment with calcitriol. This effect was not due to modulation of H2O2 degradation or to a specific effect on *OH-mediated cytotoxicity. The H2O2-induced drop in mitochondrial membrane potential and release of cytochrome c were enhanced by calcitriol. These findings indicate that calcitriol sensitizes breast cancer cells to ROS-induced death by affecting event(s) common to both caspase-dependent and -independent modes of cell death upstream to mitochondrial damage.

Alterations in mitochondria membrane potential and oxidative stress in infertile men: a prospective observational study

OBJECTIVE

To evaluate the mitochondrial membrane potential (MMP) of spermatozoa and its correlation with semen parameters and production of reactive oxygen species (ROS) in infertile men and healthy donors.

DESIGN

Controlled prospective study.

SETTING

Male infertility clinic, Glickman Urological Institute, The Cleveland Clinic Foundation, Cleveland, Ohio.

PATIENT(S)

Nineteen infertile men and 7 healthy volunteers.

INTERVENTION(S)

Standard semen analysis, assessment of MMP and ROS production in spermatozoa. The MMP was assessed by flow cytometry using the probe carbocyanine DiOC(6)(3) and ROS was measured with chemiluminescence assay using luminol.

MAIN OUTCOME MEASURE(S)

The results of MMP are reported as the median interquartile range (IQR) number of cells counted in different areas of fluorescence. Results of ROS measurement are expressed as x10(6) counted photons per minute per 20 million sperm (cpm).

RESULT(S)

The patients with abnormal semen parameters had a significantly lower MMP [1337.7 (1066.38, 1879.2)], and higher ROS [1.12 (0.26, 3.86)] than the donors [MMP: 2482.9 (2162.5, 3520.6)] and [ROS: 0.10 (0.01, 0.14)]. The MMP was positively correlated with sperm concentration (r = 0.62) and negatively correlated with the ROS produced (r = -0.45).

CONCLUSION(S)

Measuring MMP in spermatozoa provides useful information about a man's fertility potential. Increased ROS production by spermatozoa is associated with a decreased MMP.

Vitamin D enhances caspase-dependent and -independent TNFalpha-induced breast cancer cell death: The role of reactive oxygen species and mitochondria

Calcitriol, the hormonal form of vitamin D, potentiates the activity of some common anticancer drugs and agents of the anticancer immune system, including tumor necrosis factor alpha (TNFalpha). TNFalpha-induced cytotoxicity is due to both caspase-dependent and -independent pathways. Cotreatment with calcitriol enhanced both modes of TNFalpha-induced death in MCF-7 breast cancer cells. It increased caspase-3-like activity as assayed by the cleavage of poly-(ADP-ribose)polymerase and of the fluorogenic substrate ac-DEVD-AMC. It also enhanced TNFalpha-induced caspase-independent cytotoxicity in the presence of the pan-caspase inhibitor zD-2,6-dichlorobenzoyloxymethylketone. The antioxidants N-acetylcysteine, reduced glutathione, lipoic acid and ascorbic acid markedly reduced the enhancing effect of the hormone on TNFalpha-induced caspase activation. N-acetylcysteine and reduced glutathione also decreased caspase-independent cytotoxicity in the presence or absence of calcitriol, indicating that reactive oxygen species (ROS) have a key role in the cross talk between TNFalpha and calcitriol. Mitochondrial damage is common to both TNFalpha-induced caspase-dependent and -independent pathways and may underlie excessive production of ROS. Mitochondrial membrane potential (DeltaPsi) was assessed by the specific potential-sensitive fluorescent probe JC-1. The hormone augmented the drop in DeltaPsi and release of cytochrome c from mitochondria, induced by TNFalpha. The effect of calcitriol on DeltaPsi was mimicked by rotenone, which increased both the drop in DeltaPsi and caspase activation induced by TNFalpha. It is possible that the interaction of TNFalpha and calcitriol on the level of the mitochondria is the underlying mechanism responsible for the enhancement of TNFalpha-induced, ROS-mediated caspase-dependent and -independent cell death.

Oncogene expression on the syngeneic beta-cells of long-term surviving pancreatic grafts and better effects of interleukin-1 receptor (IL-1R) and IL-2Rbeta on the grafted beta-cells in LEW/Sea strain rats

Thirty-two normal LEW/Sea rats were transplanted a piece of syngeneic pancreas between the peritoneum and abdominal muscle. Among them, 17 (68%) of the 25 rats that received pancreatic transplantation at 41-50 days of age had a surviving beta-cell mass at 5.5-7.1 months after transplantation. Among the 25 rats, 12 rats injected with interleukin-1 receptor (IL-1R) and IL-2Rbeta peptides at post-transplantation showed better surviving grafts at 5.5 months' observation. Only 2 (25%) of the other 7 young rats that received a pancreatic graft at 20 days of age had a small mass at 21 days post-transplantation. Flow cytometer (FCM) analyses showed that thymus OX40(+) (CD134(+)) T-cells were increased up to 37+/-4% at the graft rejection in the 13 old rats without the IL-R peptide injections. The 7 young rats had 99% of thymus OX40(+) T-cells. However, the 12 old rats injected with the IL-R peptides showed suppressed numbers of thymus OX40(+) T-cells (8-13+/-3%). The long-term surviving, but apoptotic, grafted beta-cells were stained positively both with anti-insulin monoclonal antibody (mAb) and with anti-c-erbB-2/human epidermal growth factor receptor (HER)-2/neu mAb. Expression of a c-erb family oncogene was shown on the pancreatic graft surviving for 7.1 months. Electron microscopic analysis of the grafted beta-cells showed abnormally large beta granules and loss of functioning mitochondria in the cytoplasm. In 18 (56%) of the 32 rats, the 220-bp and 380-bp specific products of insulin-degrading enzyme (IDE) gene were amplified using the polymerase chain reaction (PCR) of the liver DNA. Among the 18 rats, 6 rats expressed 2 extra hands of 280-bp and 700-bp in a correlation with the high levels of the transforming growth factor-alpha (TGF-alpha) cDNA of 120-bp which was amplified in the quantitative reverse-transcriptase (RT)-PCR of the liver cDNA. Among the selected 11 rats, 5 rats showed large amounts of the 120-bp TGF-alpha cDNA. Host pancreatic RT-PCR showed 235-bp or 250-bp bcl-2 and 181-bp bcl-xS gene products. The bcl-2 cDNA of the host pancreas was amplified actively when the pancreatic graft was being rejected. Exceptionally, the one female injected with the IL-R peptides showed a low level of the liver TGF-alpha cDNA together with the pancreatic expressions of Bax (140-bp), bcl-2 and like interleukin converting enzyme (LICE) (318-bp) cDNA. Insulin secretion from the grafted beta-cells and IL-1beta-induced Fas-mediated apoptosis of the beta-cells were suspected to be present at the same time in the female with the best graft survival.

Oxidative Stress in Critically Ill Patients

Oxygen-derived free radicals play an important role in the development of disease in critically ill patients. Normally, oxygen free radicals are neutralized by antioxidants such as vitamin E or enzymes such as superoxide dismutase. However, in patients who require intensive care, oxygen free radicals become a problem when either a decrease in the removal or an overproduction of the radicals occurs. This oxidative stress and the damage due to it have been implicated in many diseases in critically ill patients. Many drugs and treatments now being investigated are directed toward preventing the damage from oxidative stress. The formation of reactive oxygen species, the damage caused by them, and the body’s defense system against them are reviewed. New interventions are described that may be used in critically ill patients to prevent or treat oxidative damage.

Increase in cytosolic Ca2+ levels through the activation of non-selective cation channels induced by oxidative stress causes mitochondrial depolarization leading to apoptosis-like death in Leishmania donovani promastigotes

Reactive oxygen species are important regulators of protozoal infection. Promastigotes of Leishmania donovani, the causative agent of Kala-azar, undergo an apoptosis-like death upon exposure to H2O2. The present study shows that upon activation of death response by H2O2, a dose- and time-dependent loss of mitochondrial membrane potential occurs. This loss is accompanied by a depletion of cellular glutathione, but cardiolipin content or thiol oxidation status remains unchanged. ATP levels are reduced within the first 60 min of exposure as a result of mitochondrial membrane potential loss. A tight link exists between changes in cytosolic Ca2+ homeostasis and collapse of the mitochondrial membrane potential, but the dissipation of the potential is independent of elevation of cytosolic Na+ and mitochondrial Ca2+. Partial inhibition of cytosolic Ca2+ increase achieved by chelating extracellular or intracellular Ca2+ by the use of appropriate agents resulted in significant rescue of the fall of the mitochondrial membrane potential and apoptosis-like death. It is further demonstrated that the increase in cytosolic Ca2+ is an additive result of release of Ca2+ from intracellular stores as well as by influx of extracellular Ca2+ through flufenamic acid-sensitive non-selective cation channels; contribution of the latter was larger. Mitochondrial changes do not involve opening of the mitochondrial transition pore as cyclosporin A is unable to prevent mitochondrial membrane potential loss. An antioxidant like N-acetylcysteine is able to inhibit the fall of the mitochondrial membrane potential and prevent apoptosis-like death. Together, these findings show the importance of non-selective cation channels in regulating the response of L. donovani promastigotes to oxidative stress that triggers downstream signaling cascades leading to apoptosis-like death.

Reactive oxygen species and mitochondrial diseases

A variety of diseases have been associated with excessive reactive oxygen species (ROS), which are produced mostly in the mitochondria as byproducts of normal cell respiration. The interrelationship between ROS and mitochondria suggests shared pathogenic mechanisms in mitochondrial and ROS-related diseases. Defects in oxidative phosphorylation can increase ROS production, whereas ROS-mediated damage to biomolecules can have direct effects on the components of the electron transport system. Here, we review the molecular mechanisms of ROS production and damage, as well as the existing evidence of mitochondrial ROS involvement in human diseases.

Molecular mechanisms contributing to necrotizing enterocolitis

OBJECTIVE

To examine the cellular mechanisms involved in the pathogenesis of necrotizing enterocolitis (NEC).

SUMMARY BACKGROUND DATA

Necrotizing enterocolitis is a major cause of death and complications in neonates; the cellular mechanisms responsible for NEC are unknown. The inducible form of cyclooxygenase (i.e., COX-2) is activated by the transcription factor nuclear factor (NF)-kappaB and is thought to play a role in inflammation.

METHODS

Segments of perforated and adjacent uninvolved small intestine from neonates with NEC were analyzed for COX-2 expression by immunohistochemistry. NEC was induced in weanling (18 days old) rats by occlusion of superior mesenteric vessels for 1 hour and intraluminal injection of platelet activating factor (50 micro/kg). Small intestine was harvested for protein extraction. Western immunoblot was performed to determine expression of COX-2. Gel shift assays were performed to assess NF-kappaB binding activity.

RESULTS

Immunohistochemical analysis showed increased COX-2 protein expression in the perforated intestinal sections of all 36 neonates but not in adjacent normal intestine. Increased expression of COX-2 protein and NF-kappaB binding activity was noted in the small intestine of weanling rats at 0 and 3 hours after induction of NEC.

CONCLUSIONS

Increased COX-2 expression was identified in all neonatal intestinal segments resected for perforated NEC. In addition, a coordinate induction of COX-2 expression and NF-kappaB binding was noted in a rodent model of NEC. These findings suggest that the COX-2/NF-kappaB pathway may play a role in the pathogenesis of NEC. Therapeutic agents that target this pathway may prove useful in the treatment or possible prevention of NEC.

Oxidative stress is not an obligate mediator of disease provoked by mitochondrial DNA mutations

With age, mitochondrial DNA mutations and oxidative stress increase, leading to the hypothesis that the production of reactive oxygen species causes the pathogenic effects of mitochondrial DNA mutations. We tested this hypothesis using transgenic mice that develop cardiomyopathy due to the accumulation of mitochondrial DNA mutations specifically in the heart. Surprisingly, the mechanism of pathogenesis does not involve increased oxidative stress. The amounts of DNA and protein oxidative adducts are not elevated in the transgenic heart. Neither are signs of increased oxidative stress detected by measurements of enzyme function or oxidative defense systems. Rather, we find that the mitochondrial DNA mutations induce a cytoprotective response including increases in the levels of Bcl-2 and Bfl-1, pro-survival proteins that inhibit apoptosis, and atrial natriuretic factor. Bcl-2 is elevated in nearly all cardiomyocytes before the onset of dilated cardiomyopathy. These results raise the possibility that a signaling pathway between the mitochondrion and the nucleus mediates the pathogenic effect of mitochondrial DNA mutations.

Regulation of energy metabolism in human cells in aging and diabetes: FoF(1), mtDNA, UCP, and ROS

Recent advances in bioenergetics consist of discoveries related to rotational coupling in ATP synthase (FoF(1)), uncoupling proteins (UCP), reactive oxygen species (ROS) and mitochondrial DNA (mtDNA). As shown in cloned sheep, mammalian genomes are composed of both nuclear DNA (nDNA) and maternal mtDNA. Oxidative phosphorylation (oxphos) varies greatly depending on cellular activities, and is regulated by both gene expression and the electrochemical potential difference of H(+) (Delta muH(+)). The expression of both mtDNA (by mtTFA) and nDNA for oxphos and UCP (by NRFs, etc.) is coordinated by a factor called PGC-1. The Delta muH(+) rotates an axis in FoF(1) that is regulated by inhibitors and ATP-sensitive K(+)-channels. We cultured human rho(o) cells (cells without mtDNA) in synthetic media and elucidated relationships among mtDNA, nDNA, Delta muH(+), UCPs, ROS, and apoptosis. These cells lack oxphos-dependent ROS formation and survive under conditions of high O(2). Cells cultured in the absence of ROS scavengers have proliferated for 40 years. UCPs lower Delta muH(+) and prevent ROS formation and resulting apoptosis. These results were applied to diabetology and gerontology. The pancreatic rho(o) cells did not secrete insulin, and mtDNA mutations caused diabetes, owing to the deficient Delta muH(+). Insulin resistance was closely related to UCPs and other energy regulators. The resulting high-glucose environment caused glycation of proteins and ROS-mediated apoptosis in vascular cells involved in diabetic complications. Telomeres, oxphos, and ROS are determinants in cellular aging. Cell division and ROS shortened telomeres and accelerated aging. In aged cells, Delta muH(+) was reduced by the slow respiration, and this change induced apoptosis. Cybrids made from aged cytoplasts and rho(o) cells showed that both decreased expression of nDNA, and somatic mutations of mtDNA are involved in the slowing of respiration in aged cells.