Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Selective inhibition of endogenous antioxidants with Auranofin causes mitochondrial oxidative stress which can be countered by selenium supplementation

Auranofin is a thiol-reactive gold (I)-containing compound with potential as a chemotherapeutic. Auranofin has the capacity to selectively inhibit endogenous antioxidant enzymes thioredoxin reductase (TrxR) and glutathione peroxidase (GPx), resulting in oxidative stress and the initiation of a pro-apoptotic cascade. The effect of Auranofin exposure on TrxR and GPx, and the potential for cellular protection through selenium supplementation was examined in the non-cancerous human cell line Swan-71. Auranofin exposure resulted in a concentration dependent differential inhibition of selenoprotein antioxidants. Significant inhibition of TrxR was observed at 20 nM Auranofin with inhibition of GPx from 10 µM. Significant increases in reactive oxygen species (ROS) were associated with antioxidant inhibition at Auranofin concentrations of 100 nM (TrxR inhibition) and 10 µM (TrxR and GPx inhibition), respectively. Evaluation of mitochondrial respiration demonstrated significant reductions in routine and maximal respiration at both 100 nM and 10 μM Auranofin. Auranofin treatment at concentrations of 10 μM and higher concentrations resulted in a ∼68% decrease in cellular viability and was associated with elevations in pro-apoptotic markers cytochrome c flux control factor (FCFc) at concentration of 100 nM and mitochondrial Bax at 10 μM. The supplementation of selenium (100 nM) prior to treatment had a generalized protective affect through the restoration of antioxidant activity with a significant increase in TrxR and GPx activity, a significant reduction in ROS and associated improvement in mitochondrial respiration and cellular viability (10 µM ∼48% increase). Selenium supplementation reduced the FCFc at low doses of Auranofin (<10 μM) however no effect was noted on either FCFc or Bax at concentrations above 10 μM. The inhibition of antioxidant systems in non-cancerous cells by Auranofin is strongly dose dependent, and this inhibition can be altered by selenium exposure. Therefore, Auranofin dose and the selenium status of patients are important considerations in the therapeutic use of Auranofin as an agent of chemosensitization.</p

Targeted antioxidant treatment in the placenta: a superoxide dismutase mimic plus catalase rescues trophoblast growth after oxidative challenge

Objectives: Placental oxidative stress may be important in the patho-genesis of preeclampsia, and we have previously found placental mito-chondrial and antioxidant adaptations in mild preeclampsia that mayallow these pregnancies to reach term delivery. However, clinical trials ofantioxidant treatments have been generally unsuccessful. Superoxidedismutase (SOD) converts superoxide to hydrogen peroxide (H2O2), whichis then converted to water and oxygen by catalase, forming a completesystem for the detoxification of reactive oxygen species (ROS) that may bea therapeutic target. Methods: Placental tissue was collected from preeclamptic (term n¼10,pre-term n¼6) and matched control pregnancies (term n¼10, pre-termn¼6). Gene expression was determined by qPCR. SOD activity wasmeasured in total and mitochondrial protein. Swan71 trophoblasts weretreated with the SOD mimetic MnTMPyP, catalase, and the mitochondrialinhibitor rotenone, and H2O2production and cell growth monitored. Results: In pre-term preeclamptic placentae,SOD1was downregulated(p¼0.048), and there was a reduction in total SOD activity (p¼0.045).Expression of mitochondrial-targetedSOD2was not changed; however,pre-term preeclamptic placentae had reduced mitochondrial SOD activity(p¼0.029). There were no changes in markers of SOD function in termpreeclamptic placentae. Treatment with MnTMPyP plus catalase reducedrotenone-induced H2O2production (4 hours: p¼0.001) and attenuated cellgrowth repression (10 hours: p¼0.001; 24 hours: p¼0.014). However,MnTMPyP without catalase repressed cell growth (10 hours: p¼0.004; 24hours: p¼0.002).Conclusion: SOD function was reduced in pre-term preeclampticplacentae but not those that reached term, indicating this may be a ther-apeutic target for extension of gestation.In vitrotreatment with the SODmimetic MnTMPyP plus catalase was effective in countering oxidativestress. The beneficial effect of MnTmPyP appears related to processingsuperoxide to H2O2, and requires the presence of catalase to fully detoxifyROS. Therefore, targeting relevant antioxidant systems may be critical totreatment outcomesNo Full Tex

<i>Anti-HNA-3a Alloantibodies Can Cause Differential Endothelial Damage through a Direct Neutrophil Activation Pathway</i>

Abstract INTRODUCTION: The human neutrophil antigen (HNA) 3a/b is associated with a single amino acid substitution (R 154Q polymorphism) on the first extracellular loop of choline transporter-like protein 2 (CTL2). Antibodies against HNA-3a have been associated with severe and fatal transfusion-related acute lung injury (TRALI). Epitope mapping suggests the existence of two types of HNA-3a antibodies. Type I antibodies only require first extracellular loop of the CTL2 for expression of the antigen, type II antibodies require at least the first 3 extracellular loops of CTL2 in a native configuration (i.e. expressed on a cell membrane). This study aimed to evaluate the activity of type I and type II anti-HNA-3a antibodies in an in vitro TRALI model. STUDY DESIGN &amp; METHODS: The granulocyte agglutination test (GAT) and granulocyte immunofluorescence test (GIFT) were used to confirm anti-HNA-3a activity in two donor sera (Q49 and Q50). Flow cytometry was used to confirm antibody binding to freshly isolated human or mouse neutrophils. A rabbit polyclonal antibody against an epitope in the third extracellular loop of CTL2's was coated onto the wells of an ELISA plate and neutrophil HNA-3a antigen was captured and sera tested. For the TRALI model, human lung microvascular endothelial cells (HLMVECs) were grown to confluence before being treated with lipopolysaccharide (LPS). Freshly isolated neutrophils from HNA-3aa homozygote donors were then added with 10% Q49 or Q50. Microscopic counting of Trypan blue staining was used to measure rate HLMVEC death. Significance was determined using a one-way ANOVA (p&amp;lt;0.05), followed by Dunnett's post-hoc test. RESULTS AND DISCUSSION: GAT and GIFT confirmed that both Q49 and Q50 contained an anti-HNA-3a antibody, and that neither contained antibodies against any other HNA or HLA molecules. In flow cytometry, both Q49 and Q50 bound to human neutrophils, but only Q49 bound to mouse neutrophils. In the ELISA, signal was detected only for Q49. These data provided evidence that Q49 was a type I antibody and Q50 was a type II antibody. Within the TRALI model, HLVMEC death was observed with both Q49 and Q50 only in the presence of LPS and neutrophils (Table 1). Previously reported HLMVEC permeability in the absence of neutrophils (Bayat et al. Arterioscler Thromb Vasc Biol. 2013) was not observed as in this study the outcome measured was HLMVEC death. In the present study, the effect for Q49 (type I) was significantly larger than for Q50 (type II; Table 1; p-value &amp;lt;0.0001). CONCLUSIONS: In this model, LPS and neutrophils were required for anti-HNA-3a mediated HLMVEC death thought to reflect events involved in the initiation of TRALI. The observation that type I antibodies elicited a stronger response provides a direction for further research. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare. </jats:sec

Placental mitochondrial adaptations in preeclampsia associated with progression to term delivery

Preeclampsia is a devastating pregnancy disorder. Severity varies widely, and while severe preeclampsia often requires pre-term delivery, women with mild preeclampsia may reach term with minor interventions. The mechanisms that mediate disease severity are poorly understood, but may include adaptive processes by the placenta. We aimed to establish whether in pregnancies that reached term and those that delivered pre-term, the placental response to preeclampsia was intrinsically different, and explore potential adaptive mechanisms. Hydrogen peroxide production and antioxidant activity were increased in term preeclamptic placentae, whereas pre-term preeclamptic placentae had reduced hydrogen peroxide production and reduced function of the antioxidant system superoxide dismutase compared to control placentae. Markers of mitochondrial fission/fusion, apoptosis and the expression level of mitochondrial complexes were differentially disrupted in term compared to pre-term preeclamptic placentae. Mitochondrial respiration and content were increased in term preeclamptic placentae, but mitochondria had a lower respiratory reserve capacity. Mitochondrial respiration and hydrogen peroxide production were increased in healthy term placentae after in vitro hypoxia/reoxygenation. Placentae from preeclamptic pregnancies that reached term showed multiple adaptions that were not present in pre-term preeclamptic placentae. Increased antioxidant activity, and expression of markers of mitochondrial fusion and apoptotic suppression, may relate to salvaging damaged mitochondria. Increased mitochondrial respiration may allow ongoing tissue function even with reduced respiratory efficiency in term preeclamptic pregnancies. Response after in vitro hypoxia/reoxygenation suggests that disruption of oxygen supply is key to placental mitochondrial adaptations. Reactive oxygen species signalling in term preeclamptic placentae may be at a level to trigger compensatory antioxidant and mitochondrial responses, allowing tissue level maintenance of function when there is organelle level dysfunction

Human neutrophil antigen 3 genotype impacts neutrophil-mediated endothelial cell cytotoxicity in a two-event model of TRALI

BACKGROUND: Antibodies against human neutrophil antigen (HNA)-3a are associated with severe cases of transfusion-related acute lung injury (TRALI). The HNA-3 system is located on choline transporter-like 2 (CTL-2) protein. CTL-2 is encoded by the gene SLC44A2 and a single-nucleotide polymorphism c.461G>A results in two antigens: HNA-3a and HNA-3b. Three HNA-3 genotypes/ phenotypes exist: HNA-3aa, HNA-3bb, and HNA-3ab. Two different pathways of anti-HNA-3a TRALI have been described: a two-hit neutrophil-dependent pathway and a one-hit neutrophil-independent pathway. However, it is not clear whether HNA-3ab heterozygous patients have a lower risk of anti-HNA-3a-mediated TRALI compared to HNA-3aa homozygous patients. MATERIALS AND METHODS: Healthy volunteers were genotyped for HNA-3 by real-time polymerase chain reaction, and phenotyped for HNA-3a by granulocyte immunofluorescence test (GIFT) and granulocyte agglutination test (GAT) against two donor sera containing anti-HNA-3a antibodies. The two sera were also used in in vitro models of human pulmonary microvascular endothelial cell (HLMVEC) cytotoxicity to investigate pathways of TRALI development. RESULTS: For both anti-HNA-3a sera, GIFT results matched the genotype, with a lower GIFT ratio for HNA-3ab neutrophils compared to HNA-3aa neutrophils, whereas GAT results showed no difference in agglutination. HLMVEC cytotoxicity was not observed in a one-hit neutrophil-independent model but was observed in a two-hit neutrophil-dependent model. Differences in cytotoxicity were observed between the two anti-HNA-3a sera used. Consistent with reduced HNA-3a antigen density as measured by GIFT, HNA-3ab neutrophils mediated less HLMVEC cytotoxicity than HNA-3aa neutrophils. CONCLUSION: HNA-3 genotype and HNA-3a antigen expression impacted the severity of anti-HNA-3a-mediated HLMVEC cytotoxicity in a two-hit neutrophil-dependent model of TRALI. Different HNA-3a antibodies might also impact the magnitude of HLMVEC cytotoxicity.</p

Maternal selenium deficiency during pregnancy in mice increases thyroid hormone concentrations, alters placental function and reduces fetal growth

Key points: Inappropriate intake of key micronutrients in pregnancy is known to alter maternal endocrine status, impair placental development and induce fetal growth restriction. Selenium is an essential micronutrient required for the function of approximately 25 important proteins. However, the specific effects of selenium deficiency during pregnancy on maternal, placental and fetal outcomes are poorly understood. The present study demonstrates that maternal selenium deficiency increases maternal triiodothyronine and tetraiodothyronine concentrations, reduces fetal blood glucose concentrations, and induces fetal growth restriction. Placental expression of key selenium-dependent thyroid hormone converting enzymes were reduced, whereas the expression of key placental nutrient transporters was dysregulated. Selenium deficiency had minimal impact on selenium-dependent anti-oxidants but increased placental copper concentrations and expression of superoxide dismutase 1. These results highlight the idea that selenium deficiency during pregnancy may contribute to thyroid dysfunction, causing reduced fetal growth, that may precede programmed disease outcomes in offspring. Abstract: Selenium is a trace element fundamental to diverse homeostatic processes, including anti-oxidant regulation and thyroid hormone metabolism. Selenium deficiency in pregnancy is common and increases the risk of pregnancy complications including fetal growth restriction. Although altered placental formation may contribute to these poor outcomes, the mechanism by which selenium deficiency contributes to complications in pregnancy is poorly understood. Female C57BL/6 mice were randomly allocated to control (>190 µg kg–1, n = 8) or low selenium (–1, n = 8) diets 4 weeks prior to mating and throughout gestation. Pregnant mice were killed at embryonic day 18.5 followed by collection of maternal and fetal tissue. Maternal and fetal plasma thyroid hormone concentrations were analysed, as was placental expression of key selenoproteins involved in thyroid metabolism and anti-oxidant defences. Selenium deficiency increased plasma tetraiodothyronine and triiodothyronine concentrations. This was associated with a reduction in placental expression of key selenodependent deiodinases, DIO2 and DIO3. Placental expression of selenium-dependent anti-oxidants was unaffected by selenium deficiency. Selenium deficiency reduced fetal glucose concentrations, leading to reduced fetal weight. Placental glycogen content was increased within the placenta, as was Slc2a3 mRNA expression. This is the first study to demonstrate that selenium deficiency may reduce fetal weight through increased maternal thyroid hormone concentrations, impaired placental thyroid hormone metabolism and dysregulated placental nutrient transporter expression. The study suggests that the magnitude of selenium deficiency commonly reported in pregnant women may be sufficient to impair thyroid metabolism but not placental anti-oxidant concentrations.</p

Routine Imaging or Symptomatic Follow-Up After Resection of Pancreatic Adenocarcinoma

Importance: International guidelines lack consistency in their recommendations regarding routine imaging in the follow-up after pancreatic resection for pancreatic ductal adenocarcinoma (PDAC). Consequently, follow-up strategies differ between centers worldwide. Objective: To compare clinical outcomes, including recurrence-focused treatment and survival, in patients with PDAC recurrence who received symptomatic follow-up or routine imaging after pancreatic resection in international centers affiliated with the European-African Hepato-Pancreato-Biliary Association (E-AHPBA). Design, setting, and participants: This was a prospective, international, cross-sectional study. Patients from a total of 33 E-AHPBA centers from 13 countries were included between 2020 and 2021. According to the predefined study protocol, patients who underwent PDAC resection and were diagnosed with disease recurrence were prospectively included. Patients were stratified according to postoperative follow-up strategy: symptomatic follow-up (ie, without routine imaging) or routine imaging. Exposures: Symptomatic follow-up or routine imaging in patients who underwent PDAC resection. Main outcomes and measures: Overall survival (OS) was estimated with Kaplan-Meier curves and compared using the log-rank test. To adjust for potential confounders, multivariable logistic regression was used to evaluate the association between follow-up strategy and recurrence-focused treatment. Multivariable Cox proportional hazard analysis was used to study the independent association between follow-up strategy and OS. Results: Overall, 333 patients (mean [SD] age, 65 [11] years; 184 male [55%]) with PDAC recurrence were included. Median (IQR) follow-up at time of analysis 2 years after inclusion of the last patient was 40 (30-58) months. Of the total cohort, 98 patients (29%) received symptomatic follow-up, and 235 patients (71%) received routine imaging. OS was 23 months (95% CI, 19-29 months) vs 28 months (95% CI, 24-30 months) in the groups who received symptomatic follow-up vs routine imaging, respectively (P = .01). Routine imaging was associated with receiving recurrence-focused treatment (adjusted odds ratio, 2.57; 95% CI, 1.22-5.41; P = .01) and prolonged OS (adjusted hazard ratio, 0.75; 95% CI, 0.56-.99; P = .04). Conclusion and relevance: In this international, prospective, cross-sectional study, routine follow-up imaging after pancreatic resection for PDAC was independently associated with receiving recurrence-focused treatment and prolonged OS