The interplay between BAX and BAK tunes apoptotic pore growth to control mitochondrial-DNA-mediated inflammation.

BAX and BAK are key apoptosis regulators that mediate the decisive step of mitochondrial outer membrane permeabilization. However, the mechanism by which they assemble the apoptotic pore remains obscure. Here, we report that BAX and BAK present distinct oligomerization properties, with BAK organizing into smaller structures with faster kinetics than BAX. BAK recruits and accelerates BAX assembly into oligomers that continue to grow during apoptosis. As a result, BAX and BAK regulate each other as they co-assemble into the same apoptotic pores, which we visualize. The relative availability of BAX and BAK molecules thereby determines the growth rate of the apoptotic pore and the relative kinetics by which mitochondrial contents, most notably mtDNA, are released. This feature of BAX and BAK results in distinct activation kinetics of the cGAS/STING pathway with implications for mtDNA-mediated paracrine inflammatory signaling.

DRP1 interacts directly with BAX to induce its activation and apoptosis.

The apoptotic executioner protein BAX and the dynamin-like protein DRP1 co-localize at mitochondria during apoptosis to mediate mitochondrial permeabilization and fragmentation. However, the molecular basis and functional consequences of this interplay remain unknown. Here, we show that BAX and DRP1 physically interact, and that this interaction is enhanced during apoptosis. Complex formation between BAX and DRP1 occurs exclusively in the membrane environment and requires the BAX N-terminal region, but also involves several other BAX surfaces. Furthermore, the association between BAX and DRP1 enhances the membrane activity of both proteins. Forced dimerization of BAX and DRP1 triggers their activation and translocation to mitochondria, where they induce mitochondrial remodeling and permeabilization to cause apoptosis even in the absence of apoptotic triggers. Based on this, we propose that DRP1 can promote apoptosis by acting as noncanonical direct activator of BAX through physical contacts with its N-terminal region.

Apoptotic stress induces Bax-dependent, caspase-independent redistribution of LINC complex nesprins.

The canonical function of Bcl-2 family proteins is to regulate mitochondrial membrane integrity. In response to apoptotic signals the multi-domain pro-apoptotic proteins Bax and Bak are activated and perforate the mitochondrial outer membrane by a mechanism which is inhibited by their interaction with pro-survival members of the family. However, other studies have shown that Bax and Bak may have additional, non-canonical functions, which include stress-induced nuclear envelope rupture and discharge of nuclear proteins into the cytosol. We show here that the apoptotic stimuli cisplatin and staurosporine induce a Bax/Bak-dependent degradation and subcellular redistribution of nesprin-1 and nesprin-2 but not nesprin-3, of the linker of nucleoskeleton and cytoskeleton (LINC) complex. The degradation and redistribution were caspase-independent and did not occur in Bax/Bak double knockout (DKO) mouse embryo fibroblasts (MEFs). Re-expression of Bax in Bax/Bak DKO MEFs restored stress-induced redistribution of nesprin-2 by a mechanism which requires Bax membrane localization and integrity of the α helices 5/6, and the Bcl-2 homology 3 (BH3) domain. We found that nesprin-2 interacts with Bax in close proximity to perinuclear mitochondria in mouse and human cells. This interaction requires the mitochondrial targeting and N-terminal region but not the BH3 domain of Bax. Our results identify nesprin-2 as a Bax binding partner and also a new function of Bax in impairing the integrity of the LINC complex.

Drp1 modulates mitochondrial stress responses to mitotic arrest.

Antimitotic drugs are extensively used in the clinics to treat different types of cancer. They can retain cells in a prolonged mitotic arrest imposing two major fates, mitotic slippage, or mitotic cell death. While the former is molecularly well characterized, the mechanisms that control mitotic cell death remain poorly understood. Here, we performed quantitative proteomics of HeLa cells under mitotic arrest induced with paclitaxel, a microtubule-stabilizer drug, to identify regulators of such cell fate decision. We identified alterations in several apoptosis-related proteins, among which the mitochondrial fission protein Drp1 presented increased levels. We found that Drp1 depletion during prolonged mitotic arrest led to strong mitochondrial depolarization and faster mitotic cell death as well as enhanced mitophagy, a mechanism to remove damaged mitochondria. Our findings support a new role of Drp1 in orchestrating the cellular stress responses during mitosis, where mitochondrial function and distribution into the daughter cells need to be coordinated with cell fate. This novel function of Drp1 in the cell cycle becomes best visible under conditions of prolonged mitotic arrest.

Nivel de conocimiento sobre métodos anticonceptivos y salud reproductiva en adolescentes mexicanos de medio rural / Level of knowledge about contraceptive methods and reproductive health in Mexican adolescents in rural area

INTRODUCCIÓN la información sobre anticoncepción es importante antes que se inicie la vida sexual. OBJETIVO determinar el nivel de conocimiento y uso de métodos anticonceptivos por adolescentes en medio rural. MÉTODOS estudio transversal analítico, se encuestó a adolescentes de 15-19 años de edad de ambos sexos, que asistían a un centro de salud rural, 70% sin vida sexual y 30% que ya habían iniciado su vida sexual. Se empleó una cuestionario auto-administrado que incluyó variables sociodemográficas, socioeducativas y de uso de métodos anticonceptivos. RESULTADOS el nivel de conocimientos fue medio en 38% y bajo en 31%. El condón fue el método anticonceptivo más utilizado (88%) y del que se tenía más conocimiento. Tiene un conocimiento bajo el 48,7%, el 30% y el 29,7% de adolescentes de 15, 16 y 17 años respectivamente. El conocimiento va aumentando con la edad; es "medio y alto" en 48,7% y 86,6% a los 15 y 19 años, respectivamente. Se observa que a mayor conocimiento, mayor uso de métodos anticonceptivos. CONCLUSIONES es necesaria mayor información sobre el uso adecuado de los métodos anticonceptivos en la escuela y en la familia a nivel rural antes del inicio de la vida sexual, para prevenir las enfermedades de transmisión sexual y los embarazos no deseados.

INTRODUCTION information on contraception is important before sexual life begins. OBJECTIVE to determine the level of knowledge and use of contraceptive methods by adolescents in rural areas. METHODS analytical cross-sectional study, surveyed adolescents aged 15-19 years of both sexes, who attended a rural health center, 70% without sexual life and 30% who had already started their sexual life. A self-administered questionnaire was used that included sociodemographic, socio-educational and use of contraceptive variables. RESULTS the level of knowledge was medium in 38% and low in 31%. The condom was the most widely used contraceptive method (88%) and the most widely known. 48,7%, 30%, and 29,7% of adolescents aged 15, 16, and 17, respectively, have low knowledge. Knowledge increases with age; it is "medium and high" in 48,7% and in 86,6% at 15 and 19 years, respectively. It is observed that the greater the knowledge, the more frequent use of contraceptive methods. CONCLUSIONS more information is needed on the proper use of contraceptive methods at school and in the family at the rural level before the start of sexual life, to prevent sexually transmitted diseases and unwanted pregnancies.

PARIETAL PERITONEUM GRAFT FOR DUODENUM INJURIES IN AN ANIMAL MODEL.

BACKGROUND: Duodenal injuries and their surgical procedure cause a high morbidity and mortality. AIM: To assess the overall effectiveness of the auto-graft of peritoneum in the treatment of the perforation of the duodenum, aiming to reduce surgery time, costs, complexity and mortality. METHODS: Twelve New Zealand rabbits, ages 4-6 months, both sexes, underwent designed surgical grade III duodenal injuries that were repaired 18 h after. Rabbits were surgically treated with the proposed auto-graft of peritoneum. RESULTS: No postoperative deaths were observed; the animals presented corporal weight increase and were euthanized six months later. There was no significant difference between both groups relating to the postoperative evolution or in the histological changes. CONCLUSION: Auto-graft of the peritoneum and posterior fascia is a useful option for duodenal repair and that is worth of evaluation for humans.

Parietal peritoneum graft for duodenum injuries in an animal model / Enxerto de peritônio parietal em lesão duodenal: modelo animal

ABSTRACT Background: Duodenal injuries and their surgical procedure cause a high morbidity and mortality. Aim: To assess the overall effectiveness of the auto-graft of peritoneum in the treatment of the perforation of the duodenum, aiming to reduce surgery time, costs, complexity and mortality. Methods: Twelve New Zealand rabbits, ages 4-6 months, both sexes, underwent designed surgical grade III duodenal injuries that were repaired 18 h after. Rabbits were surgically treated with the proposed auto-graft of peritoneum. Results: No postoperative deaths were observed; the animals presented corporal weight increase and were euthanized six months later. There was no significant difference between both groups relating to the postoperative evolution or in the histological changes. Conclusion: Auto-graft of the peritoneum and posterior fascia is a useful option for duodenal repair and that is worth of evaluation for humans.

RESUMO Racional: Lesões duodenais e seu procedimento cirúrgico causam alta morbimortalidade. Objetivo: Avaliar a eficácia geral de retalho peritoneal no tratamento da perfuração do duodeno, visando reduzir o tempo, os custos, a complexidade e a mortalidade cirúrgicas. Métodos: Doze coelhos da raça Nova Zelândia, com idades entre 4-6 meses, ambos os sexos, foram submetidos a lesões duodenais cirúrgicas de grau III, que foram reparadas 18 h depois. Coelhos foram tratados cirurgicamente com a proposta de auto-enxerto de peritônio. Resultados: Não foram observados óbitos pós-operatórios; os animais apresentaram aumento de peso corporal e foram eutanasiados seis meses depois. Não houve diferença significativa entre os dois grupos em relação à evolução pós-operatória ou nas alterações histológicas. Conclusão: A auto-enxertia do peritônio e da fáscia posterior é uma opção útil para o reparo duodenal e vale a pena ser avaliada em seres humanos.

The mycotoxin phomoxanthone A disturbs the form and function of the inner mitochondrial membrane.

Mitochondria are cellular organelles with crucial functions in the generation and distribution of ATP, the buffering of cytosolic Ca2+ and the initiation of apoptosis. Compounds that interfere with these functions are termed mitochondrial toxins, many of which are derived from microbes, such as antimycin A, oligomycin A, and ionomycin. Here, we identify the mycotoxin phomoxanthone A (PXA), derived from the endophytic fungus Phomopsis longicolla, as a mitochondrial toxin. We show that PXA elicits a strong release of Ca2+ from the mitochondria but not from the ER. In addition, PXA depolarises the mitochondria similarly to protonophoric uncouplers such as CCCP, yet unlike these, it does not increase but rather inhibits cellular respiration and electron transport chain activity. The respiration-dependent mitochondrial network structure rapidly collapses into fragments upon PXA treatment. Surprisingly, this fragmentation is independent from the canonical mitochondrial fission and fusion mediators DRP1 and OPA1, and exclusively affects the inner mitochondrial membrane, leading to cristae disruption, release of pro-apoptotic proteins, and apoptosis. Taken together, our results suggest that PXA is a mitochondrial toxin with a novel mode of action that might prove a useful tool for the study of mitochondrial ion homoeostasis and membrane dynamics.

Nature versus nurture? Consequences of short captivity in early stages.

Biological changes occurring as a consequence of domestication and/or captivity are not still deeply known. In Atlantic salmon (Salmo salar), endangered (Southern Europe) populations are enhanced by supportive breeding, which involves only 6 months of captive rearing following artificial spawning of wild-collected adults. In this work, we assess whether several fitness-correlated life-history traits (migratory behavior, straying rate, age at maturity, and growth) are affected by early exposure to the captive environment within a generation, before reproduction thus before genetic selection. Results showed significant differences in growth and migratory behavior (including straying), associated with this very short period of captivity in natural fish populations, changing even genetic variability (decreased in hatchery-reared adults) and the native population structure within and between rivers of the species. These changes appeared within a single generation, suggesting very short time of captivity is enough for initiating changes normally attributed to domestication. These results may have potential implications for the long-term population stability/viability of species subjected to restoration and enhancement processes and could be also considered for the management of zoo populations.

Bax, Bak and beyond - mitochondrial performance in apoptosis.

Bax and Bak are members of the Bcl-2 family and core regulators of the intrinsic pathway of apoptosis. Upon apoptotic stimuli, they are activated and oligomerize at the mitochondrial outer membrane (MOM) to mediate its permeabilization, which is considered a key step in apoptosis. However, the molecular mechanism underlying Bax and Bak function has remained a key question in the field. Here, we review recent structural and biophysical evidence that has changed our understanding of how Bax and Bak promote MOM permeabilization. We also discuss how the spatial regulation of Bcl-2 family preference for binding partners contributes to regulate Bax and Bak activation. Finally, we consider the contribution of mitochondrial composition, dynamics and interaction with other organelles to apoptosis commitment. A new perspective is emerging, in which the control of apoptosis by Bax and Bak goes beyond them and is highly influenced by additional mitochondrial components.

Differential requirements for Tousled-like kinases 1 and 2 in mammalian development.

The regulation of chromatin structure is critical for a wide range of essential cellular processes. The Tousled-like kinases, TLK1 and TLK2, regulate ASF1, a histone H3/H4 chaperone, and likely other substrates, and their activity has been implicated in transcription, DNA replication, DNA repair, RNA interference, cell cycle progression, viral latency, chromosome segregation and mitosis. However, little is known about the functions of TLK activity in vivo or the relative functions of the highly similar TLK1 and TLK2 in any cell type. To begin to address this, we have generated Tlk1- and Tlk2-deficient mice. We found that while TLK1 was dispensable for murine viability, TLK2 loss led to late embryonic lethality because of placental failure. TLK2 was required for normal trophoblast differentiation and the phosphorylation of ASF1 was reduced in placentas lacking TLK2. Conditional bypass of the placental phenotype allowed the generation of apparently healthy Tlk2-deficient mice, while only the depletion of both TLK1 and TLK2 led to extensive genomic instability, indicating that both activities contribute to genome maintenance. Our data identifies a specific role for TLK2 in placental function during mammalian development and suggests that TLK1 and TLK2 have largely redundant roles in genome maintenance.

Necroptosis Execution Is Mediated by Plasma Membrane Nanopores Independent of Calcium.

Necroptosis is a form of regulated necrosis that results in cell death and content release after plasma membrane permeabilization. However, little is known about the molecular events responsible for the disruption of the plasma membrane. Here, we find that early increase in cytosolic calcium in TNF-induced necroptosis is mediated by treatment with a Smac mimetic via the TNF/RIP1/TAK1 survival pathway. This does not require the activation of the necrosome and is dispensable for necroptosis. Necroptosis induced by the activation of TLR3/4 pathways does not trigger early calcium flux. We also demonstrate that necroptotic plasma membrane rupture is mediated by osmotic forces and membrane pores around 4 nm in diameter. This late permeabilization step represents a hallmark in necroptosis execution that is cell and treatment independent and requires the RIP1/RIP3/MLKL core. In support of this, treatment with osmoprotectants reduces cell damage in an in vivo necroptosis model of ischemia-reperfusion injury.

[Causes of under recorded in job accidents]. / Causas de subregistro de accidentes de trabajo.

OBJECTIVE: To determine causes of under-record the job accidents in the IMSS at Veracruz state. METHODS: A prospective cross-sectional study was carried out in patients with a job accident who not concluded the proceedings to established as job accident (JA) in a Primary Care Unit, from September to December, in 2005. The data were obtained from ST-4-30-8 formats at emergency room. The results were analyzed through statistical programme. RESULTS: From 587 patients having job accidents, 242 (41 %) did not complete the administrative proceeding which would mark it as an accident during their work journey, and in this group, 118 (49 %) were agree to answer the survey. Contusions and wounds predominated on diagnostic. The proceeding for job accident was not completed by patients because: 53% said that did not matter, 24 % patients had not validity in the institute, and 10 % patients had not obtained boss permission to complete proceedings. CONCLUSIONS: Patients apathy, invalidity in the institute, and lack boss permission to complete proceedings were the main reasons of under-recorded.