Linking triphenylphosphonium cation to a bicyclic hydroquinone improves their antiplatelet effect via the regulation of mitochondrial function.

Platelets are the critical target for preventing and treating pathological thrombus formation. However, despite current antiplatelet therapy, cardiovascular mortality remains high, and cardiovascular events continue in prescribed patients. In this study, first results were obtained with ortho-carbonyl hydroquinones as antiplatelet agents; we found that linking triphenylphosphonium cation to a bicyclic ortho-carbonyl hydroquinone moiety by a short alkyl chain significantly improved their antiplatelet effect by affecting the mitochondrial functioning. The mechanism of action involves uncoupling OXPHOS, which leads to an increase in mitochondrial ROS production and a decrease in the mitochondrial membrane potential and OCR. This alteration disrupts the energy production by mitochondrial function necessary for the platelet activation process. These effects are responsive to the complete structure of the compounds and not to isolated parts of the compounds tested. The results obtained in this research can be used as the basis for developing new antiplatelet agents that target mitochondria.

Mitochondrial function and reactive oxygen species production during human sperm capacitation: Unraveling key players.

Sperm capacitation is a critical process for male fertility. It involves a series of biochemical and physiological changes that occur in the female reproductive tract, rendering the sperm competent for successful fertilization. The precise mechanisms and, specifically, the role of mitochondria, in sperm capacitation remain incompletely understood. Previously, we revealed that in mouse sperm mitochondrial activity (e.g., oxygen consumption, membrane potential, ATP/ADP exchange, and mitochondrial Ca2+ ) increases during capacitation. Herein, we studied mitochondrial function by high-resolution respirometry (HRR) and reactive oxygen species production in capacitated (CAP) and non-capacitated (NC) human spermatozoa. We found that in capacitated sperm from normozoospermic donors, the respiratory control ratio increased by 36%, accompanied by a double oxygen consumption rate (OCR) in the presence of antimycin A. Extracellular hydrogen peroxide (H2 O2 ) detection was three times higher in CAP than in NC sperm cells. To confirm that H2 O2 production depends on mitochondrial superoxide ( O 2 · - $$ {\mathrm{O}}_2^{\cdotp -} $$ ) formation, we evaluated mitochondrial aconitase (ACO2) amount, activity, and role in the metabolic flux from the sperm tricarboxylic acid cycle. We estimated that CAP cells produce, on average by individual, (59 ± 22)% more O 2 · - $$ {\mathrm{O}}_2^{\cdotp -} $$ in the steady-state compared to NC cells. Finally, we analyzed two targets of oxidative stress: lipid peroxidation by western blot against 4-hydroxynonenal and succinate dehydrogenase (SDH) activity by HRR. We did not observe modifications in lipoperoxidation nor the activity of SDH, suggesting that during capacitation, the increase in mitochondrial H2 O2 production does not damage sperm and it is necessary for the normal CAP process.

Trombosis venosa y de senos cerebrales en recién nacidos y niños / Venous and cerebral sinus thrombosis in newborns and children

Resumen Introducción : La trombosis de venas y senos venosos cerebrales (TVSC) constituye una causa conocida, aun que subestimada de ictus en la infancia. Su diagnóstico requiere un alto índice de sospecha, una correcta in terpretación de la neuroimagen e interrelación entre el clínico y el radiólogo. Objetivo : Analizar las manifestaciones clínicas, fac tores de riesgo y neuroimagen de recién nacidos (RN) y niños menores de 15 años con TVSC. Métodos: Estudio descriptivo, retrospectivo, multi céntrico, de una serie consecutiva de casos de menores de 15 años que ingresaron por TVSC entre el 1 de enero del 2010 y el 1 de marzo de 2022. Resultados : El estudio incluyó 51 pacientes: 39% con síntomas agudos y 59% subagudos. En los RN predomi naron síntomas encefalopáticos y convulsiones, mien tras en los niños elementos de hipertensión endocranea na (HTEC). Se identificaron factores de riesgo en el 90% de los casos. La resonancia magnética con angiografía en tiempo venoso confirmó el diagnóstico en el 80%, siendo el seno recto el más afectado en RN y el seno lateral en niños. Se encontraron complicaciones hemorrágicas en 30.5%, siendo más frecuentes en los RN. Se inició anti coagulación en el 82% sin complicaciones. Las secuelas estuvieron presentes en 44.4% de RN y 37.9% de niños, siendo más frecuentes y graves en los RN. Conclusiones : Para realizar un diagnóstico precoz es fundamental pensar en TVSC en RN con síntomas en cefalopáticos y/o convulsiones y en mayores con clínica de HTEC en presencia de enfermedades predisponentes o desencadenantes.

Abstract Introduction : Cerebral venous sinus thrombosis (CVST) is a well-known, although underestimated, cause of stroke in childhood. Its diagnosis requires a high index of suspicion, a correct interpretation of neuroim aging studies and an interrelation between clinicians and radiologists. The clinical features, risk factors and neuroimaging of children under 15 years of age with CVST were analyzed. Methods : multicenter, retrospective, descriptive, study of a consecutive series of cases of children under 15 years of age, who were admitted due to CVST between January 1st, 2010, and March 1st, 2022. Results : The study included 51 patients: 39% with acute symptoms and 59% with subacute symptoms. Newborns predominantly presented encephalopathic symptoms and seizures, while children exhibited signs of intracranial hypertension (ICH). Risk factors were 96 identified in 90% of the cases. Magnetic resonance with angiography in venous time confirmed the diagnosis in 80% of the patients, with the straight sinus being the most affected in newborns and the lateral sinus in chil dren. Hemorrhagic complications were found in 30.5%, being more frequent in newborns. Anticoagulation was initiated in 82% without complications. Sequelae were present in 44.4% of newborns and 37.9% of children, being more frequent and severe in newborns. Conclusions : To make an early diagnosis, it is essen tial to consider CVST in newborns with encephalopathic symptoms and/or seizures, and in children with signs of ICH in the presence of predisposing or triggering conditions.

[Venous and cerebral sinus thrombosis in newborns and children]. / Trombosis venosa y de senos cerebrales en recién nacidos y niños.

INTRODUCTION: Cerebral venous sinus thrombosis (CVST) is a well-known, although underestimated, cause of stroke in childhood. Its diagnosis requires a high index of suspicion, a correct interpretation of neuroimaging studies and an interrelation between clinicians and radiologists. The clinical features, risk factors and neuroimaging of children under 15 years of age with CVST were analyzed. METHODS: multicenter, retrospective, descriptive, study of a consecutive series of cases of children under 15 years of age, who were admitted due to CVST between January 1st, 2010, and March 1st, 2022. RESULTS: The study included 51 patients: 39% with acute symptoms and 59% with subacute symptoms. Newborns predominantly presented encephalopathic symptoms and seizures, while children exhibited signs of intracranial hypertension (ICH). Risk factors were identified in 90% of the cases. Magnetic resonance with angiography in venous time confirmed the diagnosis in 80% of the patients, with the straight sinus being the most affected in newborns and the lateral sinus in children. Hemorrhagic complications were found in 30.5%, being more frequent in newborns. Anticoagulation was initiated in 82% without complications. Sequelae were present in 44.4% of newborns and 37.9% of children, being more frequent and severe in newborns. CONCLUSIONS: To make an early diagnosis, it is essential to consider CVST in newborns with encephalopathic symptoms and/or seizures, and in children with signs of ICH in the presence of predisposing or triggering conditions.

Introducción: La trombosis de venas y senos venosos cerebrales (TVSC) constituye una causa conocida, aunque subestimada de ictus en la infancia. Su diagnóstico requiere un alto índice de sospecha, una correcta interpretación de la neuroimagen e interrelación entre el clínico y el radiólogo. OBJETIVO: Analizar las manifestaciones clínicas, factores de riesgo y neuroimagen de recién nacidos (RN) y niños menores de 15 años con TVSC. Métodos: Estudio descriptivo, retrospectivo, multicéntrico, de una serie consecutiva de casos de menores de 15 años que ingresaron por TVSC entre el 1 de enero del 2010 y el 1 de marzo de 2022. RESULTADOS: El estudio incluyó 51 pacientes: 39% con síntomas agudos y 59% subagudos. En los RN predominaron síntomas encefalopáticos y convulsiones, mientras en los niños elementos de hipertensión endocraneana (HTEC). Se identificaron factores de riesgo en el 90% de los casos. La resonancia magnética con angiografía en tiempo venoso confirmó el diagnóstico en el 80%, siendo el seno recto el más afectado en RN y el seno lateral en niños. Se encontraron complicaciones hemorrágicas en 30.5%, siendo más frecuentes en los RN. Se inició anticoagulación en el 82% sin complicaciones. Las secuelas estuvieron presentes en 44.4% de RN y 37.9% de niños, siendo más frecuentes y graves en los RN. CONCLUSIONES: Para realizar un diagnóstico precoz es fundamental pensar en TVSC en RN con síntomas encefalopáticos y/o convulsiones y en mayores con clínica de HTEC en presencia de enfermedades predisponentes o desencadenantes.

The Use of Triphenyl Phosphonium Cation Enhances the Mitochondrial Antiplatelet Effect of the Compound Magnolol.

Although platelets are anucleated cells, they have fully functional mitochondria, and currently, it is known that several processes that occur in the platelet require the action of mitochondria. There are plenty of mitochondrial-targeted compounds described in the literature related to cancer, however, only a small number of studies have approached their interaction with platelet mitochondria and/or their effects on platelet activity. Recent studies have shown that magnolia extract and mitochondria-targeted magnolol can inhibit mitochondrial respiration and cell proliferation in melanoma and oral cancer cells, respectively, and they can also induce ROS and mitophagy. In this study, the effect of triphenylphosphonium cation, linked by alkyl chains of different lengths, to the organic compound magnolol on human-washed platelets was evaluated. We demonstrated that the addition of triphenylphosphonium by a four-carbon linker to magnolol (MGN4) considerably enhanced the Magnolol antiplatelet effect by a 3-fold decrease in the IC50. Additionally, platelets exposed to MGN4 5 µM showed several differences from the control including increased basal respiration, collagen-induced respiration, ATP-independent respiration, and reduced ATP-dependent respiration and non-mitochondrial respiration.

Computational and mitochondrial functional studies of novel compound heterozygous variants in SPATA5 gene support a causal link with epileptogenic encephalopathy.

The SPATA5 gene encodes a 892 amino-acids long protein that has a putative mitochondrial targeting sequence and has been proposed to function in maintenance of mitochondrial function and integrity during mouse spermatogenesis. Several studies have associated homozygous or compound heterozygous mutations in SPATA5 gene to microcephaly, intellectual disability, seizures and hearing loss. This suggests a role of the SPATA5 gene also in neuronal development. Recently, our group presented results validating the use of blood cells for the assessment of mitochondrial function for diagnosis and follow-up of mitochondrial disease, minimizing the need for invasive procedures such as muscle biopsy. In this study, we were able to diagnose a patient with epileptogenic encephalopathy using next generation sequencing. We found two novel compound heterozygous variants in SPATA5 that are most likely causative. To analyze the impact of SPATA5 mutations on mitochondrial functional studies directly on the patients' mononuclear cells and platelets were undertaken. Oxygen consumption rates in platelets and PBMCs were impaired in the patient when compared to a healthy control. Also, a decrease in mitochondrial mass was observed in the patient monocytes with respect to the control. This suggests a true pathogenic effect of the mutations in mitochondrial function, especially in energy production and possibly biogenesis, leading to the observed phenotype.

Redox sensitive human mitochondrial aconitase and its interaction with frataxin: In vitro and in silico studies confirm that it takes two to tango.

Mitochondrial aconitase (ACO2) has been postulated as a redox sensor in the tricarboxylic acid cycle. Its high sensitivity towards reactive oxygen and nitrogen species is due to its particularly labile [4Fe-4S]2+ prosthetic group which yields an inactive [3Fe-4S]+ cluster upon oxidation. Moreover, ACO2 was found as a main oxidant target during aging and in pathologies where mitochondrial dysfunction is implied. Herein, we report the expression and characterization of recombinant human ACO2 and its interaction with frataxin (FXN), a protein that participates in the de novo biosynthesis of Fe-S clusters. A high yield of pure ACO2 (≥99%, 22 ± 2 U/mg) was obtained and kinetic parameters for citrate, isocitrate, and cis-aconitate were determined. Superoxide, carbonate radical, peroxynitrite, and hydrogen peroxide reacted with ACO2 with second-order rate constants of 108, 108, 105, and 102 M-1 s-1, respectively. Temperature-induced unfolding assessed by tryptophan fluorescence of ACO2 resulted in apparent melting temperatures of 51.1 ± 0.5 and 43.6 ± 0.2 °C for [4Fe-4S]2+ and [3Fe-4S]+ states of ACO2, sustaining lower thermal stability upon cluster oxidation. Differences in protein dynamics produced by the Fe-S cluster redox state were addressed by molecular dynamics simulations. Reactivation of [3Fe-4S]+-ACO2 by FXN was verified by activation assays and direct iron-dependent interaction was confirmed by protein-protein interaction ELISA and fluorescence spectroscopic assays. Multimer modeling and protein-protein docking predicted an ACO2-FXN complex where the metal ion binding region of FXN approaches the [3Fe-4S]+ cluster, supporting that FXN is a partner for reactivation of ACO2 upon oxidative cluster inactivation.

Blood cell respiration rates and mtDNA copy number: A promising tool for the diagnosis of mitochondrial disease.

Human mitochondrial diseases are a group of heterogeneous diseases caused by defects in oxidative phosphorylation, due to mutations in mitochondrial (mtDNA) or nuclear DNA. The diagnosis of mitochondrial disease is challenging since mutations in multiple genes can affect mitochondrial function, there is considerable clinical variability and a poor correlation between genotype and phenotype. Herein we assessed mitochondrial function in peripheral blood mononuclear cells (PBMCs) and platelets from volunteers without known metabolic pathology and patients with mitochondrial disease. Oxygen consumption rates were evaluated and respiratory parameters indicative of mitochondrial function were obtained. A negative correlation between age and respiratory parameters of PBMCs from control individuals was observed. Surprisingly, respiratory parameters of PBMCs normalized by cell number were similar in patients and young controls. Considering possible compensatory mechanisms, mtDNA copy number in PBMCs was quantified and an increase was found in patients with respect to controls. Hence, respiratory parameters normalized by mtDNA copy number were determined, and in these conditions a decrease in maximum respiration rate and spare respiratory capacity was observed in patients relative to control individuals. In platelets no decay was seen in mitochondrial function with age, while a reduction in basal, ATP-independent and ATP-dependent respiration normalized by cell number was detected in patients compared to control subjects. In summary, our results offer promising perspectives regarding the assessment of mitochondrial function in blood cells for the diagnosis of mitochondrial disease, minimizing the need for invasive procedures such as muscle biopsies, and for following disease progression and response to treatments.

The protein disulphide isomerase inhibitor CxxCpep modulates oxidative burst and mitochondrial function in platelets.

BACKGROUND: We have previously described CxxCpep, a peptide with anti-platelet properties that inhibits peri/epicellular protein disulphide isomerase (pecPDI) by forming a mixed disulfide bond with Cys400 within the pecPDI active site. OBJECTIVES: Here we sought to determine if pecPDI targeted by CxxCpep is relevant to redox mechanisms downstream of the collagen receptor GPVI in platelets. METHODS AND RESULTS: Restriction of effects of CxxCpep to the platelet surface was confirmed by LC-MS/MS following cell fractionation. Platelet aggregation was measured in platelet-rich plasma (PRP) incubated with 30 µM CxxCpep or vehicle. CxxCpep inhibited collagen-induced platelet aggregation but exerted no effect in TRAP-6-stimulated platelets. PRP was incubated with DCFDA to measure oxidative burst upon platelet adhesion to collagen. Results showed that CxxCpep decreased oxidative burst in platelets adhered to immobilized collagen while the number of adherent cells was unaffected. Furthermore, flow cytometry studies using a FITC-maleimide showed that the GPVI agonist CRP stimulated an increase in free thiols on the platelet outer membrane, which was inhibited by CxxCpep. Finally, CxxCpep inhibited platelet mitochondrial respiration upon activation with collagen, but not with thrombin. CONCLUSIONS: Our data suggest that pecPDI is a potential modulator of GPVI-mediated redox regulation mechanisms and that CxxCpep can be further exploited as a template for new antiplatelet compounds.

Aconitases: Non-redox Iron-Sulfur Proteins Sensitive to Reactive Species.

Mammalian aconitases (mitochondrial and cytosolic isoenzymes) are unique iron-sulfur cluster-containing proteins in which the metallic center participates in the catalysis of a non-redox reaction. Within the cubane iron-sulfur cluster of aconitases only three of the four iron ions have cysteine thiolate ligands; the fourth iron ion (Feα) is solvent exposed within the active-site pocket and bound to oxygen atoms from either water or substrates to be dehydrated. The catalyzed reaction is the reversible isomerization of citrate to isocitrate with an intermediate metabolite, cis-aconitate. The cytosolic isoform of aconitase is a moonlighting enzyme; when intracellular iron is scarce, the complete disassembly of the iron-sulfur cluster occurs and apo-aconitase acquires the function of an iron responsive protein and regulates the translation of proteins involved in iron metabolism. In the late 1980s and during the 1990s, cumulative experimental evidence pointed out that aconitases are main targets of reactive oxygen and nitrogen species such as superoxide radical (O2•-), hydrogen peroxide (H2O2), nitric oxide (•NO), and peroxynitrite (ONOO-). These intermediates are capable of oxidizing the cluster, which leads to iron release and consequent loss of the catalytic activity of aconitase. As the reaction of the Fe-S cluster with O2•- is fast (∼107 M-1 s-1), quite specific, and reversible in vivo, quantification of active aconitase has been used to evaluate O2•- formation in cells. While •NO is modestly reactive with aconitase, its reaction with O2•- yields ONOO-, a strong oxidant that readily leads to the disruption of the Fe-S cluster. In the case of cytosolic aconitase, it has been seen that H2O2 and •NO promote activation of iron responsive protein activity in cells. Proteomic advances in the 2000s confirmed that aconitases are main targets of reactive species in cellular models and in vivo, and other post-translational oxidative modifications such as protein nitration and carbonylation have been detected. Herein, we (1) outline the particular structural features of aconitase that make these proteins specific targets of reactive species, (2) characterize the reactions of O2•-, H2O2, •NO, and ONOO- and related species with aconitases, (3) discuss how different oxidative post-translational modifications of aconitase impact the different functions of aconitases, and (4) argue how these proteins might function as redox sensors within different cellular compartments, regulating citrate concentration and efflux from mitochondria, iron availability in the cytosol, and cellular oxidant production.

Deep sequencing discovery of causal mtDNA mutations in a patient with unspecific neurological disease.

Mitochondrial diseases (MD) are a group of diseases that can be caused by either mutations in the mitochondrial genome or nuclear DNA. MD may be difficult to diagnose since very often they are highly heterogeneous and with overlapping phenotypes. Molecular genomics approaches, especially NGS have helped in this sense. In this study we have sequenced the mitochondrial genome of a girl with an unspecific neurological disorder and her mother. The later, while neurologically unaffected, suffers from a myopathy without clear cause. We were able to detect two non-synonymous mutations in the MT-ATP6 gene, which we propose are strong candidates for causative agents. 9017C as the main candidate present at high heteroplasmy frequency in the patient (83,2%) and moderate in the mother (45,4%) while it has a low frequency in the general population. It might act alone or in conjunction with 9010A as an accessory mutation. Evolutionary analysis showed that both mutations were located in a critical position in the F0 a subunit, from F0-F1 ATPase. Functional studies showed that carriers of those mutations in comparison to an unaffected individual (father) presented a decrease in the basal and ATP-dependent oxygen consumption rate and a decrease in the maximum respiration rate.