Pneumoperitoneum, pneumoretroperitoneum and pneumomediastinum: rare complications of perforation peritonitis: a case report

BACKGROUND

Gas extravasation complications arising from perforated diverticulitis are common but manifestations such as pneumoperitoneum, pneumoretroperitoneum, and pneumomediastinum happening at the same time are exceedingly rare. This case report explores the unique presentation of these 3 complications occurring simultaneously, their diagnosis and their management, emphasizing the importance of interdisciplinary collaboration for accurate diagnosis and effective management.

CASE PRESENTATION

A 74-year-old North African female, with a medical history including hypertension, dyslipidemia, type 2 diabetes, goiter, prior cholecystectomy, and bilateral total knee replacement, presented with sudden-onset pelvic pain, chronic constipation, and rectal bleeding. Clinical examination revealed hemodynamic instability, hypoxemia, and diffuse tenderness. After appropriate fluid resuscitation with norepinephrine and saline serum, the patient was stable enough to undergo computed tomography scan. Emergency computed tomography scan confirmed perforated diverticulitis at the rectosigmoid junction, accompanied by the unprecedented presence of pneumoperitoneum, pneumoretroperitoneum, and pneumomediastinum. The patient underwent prompt surgical intervention with colo-rectal resection and a Hartmann colostomy. The postoperative course was favorable, leading to discharge one week after admission.

CONCLUSIONS

This case report highlights the clinical novelty of gas extravasation complications in perforated diverticulitis. The unique triad of pneumoperitoneum, pneumoretroperitoneum, and pneumomediastinum in a 74-year-old female underscores the diagnostic challenges and the importance of advanced imaging techniques. The successful collaboration between radiologists and surgeons facilitated a timely and accurate diagnosis, enabling a minimally invasive surgical approach. This case contributes to the understanding of atypical presentations of diverticulitis and emphasizes the significance of interdisciplinary teamwork in managing such rare manifestations.

Inhibition of autophagy rescues HT22 hippocampal neurons from erastin-induced ferroptosis

Ferroptosis is a regulated form of cell death which is considered an oxidative iron-dependent process. The lipid hydroperoxidase glutathione peroxidase 4 prevents the iron (Fe²⁺)-dependent formation of toxic lipid reactive oxygen species. While emerging evidence indicates that inhibition of glutathione peroxidase 4 as a hallmark of ferroptosis in many cancer cell lines, the involvement of this biochemical pathway in neuronal death remains largely unclear. Here, we investigate, first whether the ferroptosis key players are involved in the neuronal cell death induced by erastin. The second objective was to examine whether there is a cross talk between ferroptosis and autophagy. The third main was to address neuron response to erastin, with a special focus on ferritin and nuclear receptor coactivator 4-mediated ferritinophagy. To test this in neurons, erastin (0.5-8 µM) was applied to hippocampal HT22 neurons for 16 hours. In addition, cells were cultured with the autophagy inhibitor, 3-methyladenin (10 mM) and/or ferroptosis inhibitors, ferrostatin 1 (10-20 µM) or deferoxamine (10-200 µM) before exposure to erastin. In this study, we demonstrated by immunofluorescence and western blot analysis, that erastin downregulates dramatically the expression of glutathione peroxidase 4, the sodium-independent cystine-glutamate antiporter and nuclear receptor coactivator 4. The protein levels of ferritin and mitochondrial ferritin in HT22 hippocampal neurons did not remarkably change following erastin treatment. In addition, we demonstrated that not only the ferroptosis inhibitor, ferrostatin1/deferoxamine abrogated the ferroptotic cell death induced by erastin in hippocampal HT22 neurons, but also the potent autophagy inhibitor, 3-methyladenin. We conclude that (1) erastin-induced ferroptosis in hippocampal HT22 neurons, despite reduced nuclear receptor coactivator 4 levels, (2) that either nuclear receptor coactivator 4-mediated ferritinophagy does not occur or is of secondary importance in this model, (3) that ferroptosis seems to share some features of the autophagic cell death process.

Cerebral ischemia induced iron deposit, ferritin accumulation, nuclear receptor coactivator 4-depletion and ferroptosis

BACKGROUND

The neuronal death upon cerebral ischemia shares not only characteristics of necrosis, apoptosis and autophagy, but exhibits also biochemical and morphological characteristics of ferroptosis. Ferroptosis is a regulated form of cell death which is considered to be an oxidative iron-dependent process. It is now commonly accepted that iron and free radicals are considered to cause lipid peroxidation as well as the oxidation of proteins and nucleic acids, leading to increased membrane and enzymatic dysfunction, and finally contributing to cell death. Although ferroptosis was first described in cancer cells, emerging evidence now links mechanisms of ferroptosis to many different diseases, including cerebral ischemia.

METHODS

The objective of this study was to identify the ferroptosis key players and the underlying biochemical pathways leading to cell death upon focal cerebral ischemia in mice by using immunofluorescence, Western blotting, histochemistry and densitometry.

RESULTS

In this study, we demonstrated that cerebral ischemia induced iron-deposition, down-regulated dramatically the expression of the glutathione peroxidase 4 (GPX4), decreased the expression of the nuclear receptor coactivator 4 (NCOA4) and induced inappropriate accumulation of ferritin in the ischemic brain. This supports the hypothesis that an ischemic insult may induce ferroptosis through inhibition of GPX4.

CONCLUSION

We conclude that iron excess following cerebral ischemia leads to cell death despite activation of compensatory mechanisms for iron homeostasis, as illustrated by the accumulation of ferritins. These data emphasize the presence of a cellular mechanism that allows neuronal cells to handle restriction in iron overload.

Exacerbated Age-Related Hippocampal Alterations of Microglia Morphology, β-Amyloid and Lipofuscin Deposition and Presenilin Overexpression in Per1-/--Mice

In humans, alterations of circadian rhythms and autophagy are linked to metabolic, cardiovascular and neurological dysfunction. Autophagy constitutes a specific form of cell recycling in many eukaryotic cells. Aging is the principal risk factor for the development of neurodegenerative diseases. Thus, we assume that both the circadian clock and autophagy are indispensable to counteract aging. We have previously shown that the hippocampus of Per1^−/−-mice exhibits a reduced autophagy and higher neuronal susceptibility to ischemic insults compared to wild type (WT). Therefore, we chose to study the link between aging and loss of clock gene Per1^−/−-mice. Young and aged C3H- and Per1^−/−-mice were used as models to analyze the hippocampal distribution of Aβ42, lipofuscin, presenilin, microglia, synaptophysin and doublecortin. We detected several changes in the hippocampus of aged Per1^−/−-mice compared to their wild type littermates. Our results show significant alterations of microglia morphology, an increase in Aβ42 deposition, overexpression of presenilin, decrease in synaptophysin levels and massive accumulation of lipofuscin in the hippocampus of 24-month-old Per1^−/−-mice, without alteration of adult neurogenesis. We suggest that the marked lipofuscin accumulation, Aβ42 deposition, and overexpression of presenilin-2 observed in our experiments may be some of the consequences of the slowed autophagy in the hippocampus of aged Per1^−/−-mice. This may lead during aging to excessive accumulation of misfolded proteins which may, consequently, result in higher neuronal vulnerability.

Inhibition of Autophagy Potentiated Hippocampal Cell Death Induced by Endoplasmic Reticulum Stress and its Activation by Trehalose Failed to be Neuroprotective

INTRODUCTION

Endoplasmic reticulum (ER) stress induced the mobilization of two protein breakdown routes, the proteasomal- and autophagy-associated degradation. During ERassociated degradation, unfolded ER proteins are translocated to the cytosol where they are cleaved by the proteasome. When the accumulation of misfolded or unfolded proteins excels the ER capacity, autophagy can be activated in order to undertake the degradative machinery and to attenuate the ER stress. Autophagy is a mechanism by which macromolecules and defective organelles are included in autophagosomes and delivered to lysosomes for degradation and recycling of bioenergetics substrate.

MATERIALS AND METHODS

Autophagy upon ER stress serves initially as a protective mechanism, however when the stress is more pronounced the autophagic response will trigger cell death. Because autophagy could function as a double edged sword in cell viability, we examined the effects autophagy modulation on ER stress-induced cell death in HT22 murine hippocampal neuronal cells. We investigated the effects of both autophagy-inhibition by 3-methyladenine (3-MA) and autophagy-activation by trehalose on ER-stress induced damage in hippocampal HT22 neurons. We evaluated the expression of ER stress- and autophagy-sensors as well as the neuronal viability.

RESULTS AND CONCLUSION

Based on our findings, we conclude that under ER-stress conditions, inhibition of autophagy exacerbates cell damage and induction of autophagy by trehalose failed to be neuroprotective.

Melatonin modulates daytime-dependent synaptic plasticity and learning efficiency

Mechanisms of hippocampus-related memory formation are time-of-day-dependent. While the circadian system and clock genes are related to timing of hippocampal mnemonic processes (acquisition, consolidation, and retrieval of long-term memory [LTM]) and long-term potentiation (LTP), little is known about temporal gating mechanisms. Here, the role of the neurohormone melatonin as a circadian time cue for hippocampal signaling and memory formation was investigated in C3H/He wildtype (WT) and melatonin receptor-knockout ( MT 1 / 2 - / - ) mice. Immunohistochemical and immunoblot analyses revealed the presence of melatonin receptors on mouse hippocampal neurons. Temporal patterns of time-of-day-dependent clock gene protein levels were profoundly altered in MT 1 / 2 - / - mice compared to WT animals. On the behavioral level, WT mice displayed better spatial learning efficiency during daytime as compared to nighttime. In contrast, high error scores were observed in MT 1 / 2 - / - mice during both, daytime and nighttime acquisition. Day-night difference in LTP, as observed in WT mice, was absent in MT 1 / 2 - / - mice and in WT animals, in which the sympathetic innervation of the pineal gland was surgically removed to erase rhythmic melatonin synthesis. In addition, treatment of melatonin-deficient C57BL/6 mice with melatonin at nighttime significantly improved their working memory performance at daytime. These results illustrate that melatonin shapes time-of-day-dependent learning efficiency in parallel to consolidating expression patterns of clock genes in the mouse hippocampus. Our data suggest that melatonin imprints a time cue on mouse hippocampal signaling and gene expression to foster better learning during daytime.

Trehalase localization in the cerebral cortex, hippocampus and cerebellum of mouse brains

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Morphological localization of trehalase in vivo in the mouse brain.

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Exclusive expression of trehalase in neurons.

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Astrocytes do not express trehalase.

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A strong trehalase-immunoreactivity of trehalase was found in the perikarya and dendrites of neurons.

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Trehalase levels in neurons should have a physiological significance.

The non-reducing disaccharide trehalose is biosynthesized in several species but not in vertebrates. However, trehalase, the enzyme required for its cleavage, has been observed in different mammalian organs. Even in humans, trehalase was detected in the gastrointestinal tract and the kidney. Trehalase is an intrinsic glycoprotein of the small intestine and kidney that transports trehalose and hydrolyses it to two glucose molecules. To our knowledge, no information is available about the in vivo distribution and localization of trehalase in the mammalian brain. Here, we report the occurrence and distribution of trehalase in vivo in the mouse brain using Western blotting and immunohistochemical techniques. Using an antibody against trehalase, we demonstrated that the enzyme showed a band with a molecular mass of approx. 70 kDa in the hippocampus, cerebral cortex, cerebellum and olfactory bulbs. Strong trehalase immunoreactivity was found in the perikarya and dendrites of neurons located in the hippocampus, cerebral cortex, Purkinje cells and mitral cells. Interestingly, Purkinje cells of the cerebellum showed higher immunoreactivity than neurons in the hippocampus and cerebral cortex. The distribution of trehalase appeared to be mainly related to neurons and was not detected in astrocytes. Independent of the presence of trehalose in neurons, the trehalase levels in neurons should have physiological significance. Investigating whether the interactions between trehalose and trehalase act on brain energy metabolism or have other not-yet-identified effects would also be interesting.

The Hippocampal Autophagic Machinery is Depressed in the Absence of the Circadian Clock Protein PER1 that may Lead to Vulnerability During Cerebral Ischemia

BACKGROUND

Autophagy is an intracellular bulk self-degrading process in which cytoplasmic contents of abnormal proteins and excess or damaged organelles are sequestered into autophagosomes, and degraded upon fusion with lysosomes. Although autophagy is generally considered to be pro-survival, it also functions in cell death processes. We recently reported on the hippocampal, higher vulnerability to cerebral ischemia in mice lacking the circadian clock protein PERIOD1 (PER1), a phenomenon we found to be linked to a PER1-dependent modulation of the expression patterns of apoptotic/autophagic markers.

METHODS

To exclude the contribution of vascular or glial factors to the innate vulnerability of Per1 knockout-mice (Per1-/--mice) to cerebral ischemia in vivo, we compared the autophagic machinery between primary hippocampal cultures from wild-type (WT)- and Per1-/--mice, using the lipophilic macrolide antibiotic, Rapamycin to induce autophagy.

RESULTS

Development of autophagy in WT cells involved an increased LC3-II-to-LC3-I ratio (microtubule-associated protein 1 light chain 3) and an overall increase in the level of LC3-II. In addition, immunostaining of LC3 in WT cells revealed the typical transformation of LC3 localization from a diffused staining to a dot- and ring-like pattern. In contrast, Per1-/--hippocampal cells were resistant to Rapamycin induced alterations of autophagy hallmarks.

CONCLUSION

Our in vitro data suggests that basal activity of autophagy seems to be modulated by PER1, and confirms the in vivo data by showing that the autophagic machinery is depressed in Per1-/--hippocampal neurons.The implication of both autophagy and circadian dysfunction in the pathogenesis of cerebral ischemia suggests that a functional connection between the two processes may exist.

Exclusive Activation of Caspase-3 in Mossy Fibers and Altered Dynamics of Autophagy Markers in the Mice Hippocampus upon Status Epilepticus Induced by Kainic Acid

Epileptic seizures are generally associated with pathological changes in the hippocampus such as astrogliosis, mossy fiber sprouting, and neuronal damage. However, more than 30% of temporal lobe epilepsy in humans shows neither neuronal damage nor mossy fiber sprouting despite chronic epileptic seizures. A similar situation exists in certain commonly used strains of mice, specifically C57BL/6 and BALB/c, which exhibit epileptic seizures, but no neuronal damage upon kainic acid administration. This suggests that intrinsic factors may influence the pathological manifestations of epilepsy. Mechanisms which are behind the resistance of hippocampal cells to KA-induced neuronal death are unknown. Autophagy seems to be involved in the pathogenesis of many brain insults and to have a dual nature in neuroprotection and cell death. This study addresses the role of autophagy upon status epilepticus (SE) that has been induced by kainic acid (KA) in the C57BL/6 strain which is classified as seizure resistant. We analyzed the dynamics in the expression of autophagic and cell death markers in the hippocampus upon SE. Immunofluorescence data show that KA did not induce neuronal death in the hippocampal CA1-CA3 subfields; however, it leads to an exclusive activation of caspase-3 in the mossy fibers. We also found alterations in the expression of core proteins of the autophagic machinery. Levels of MAP1LC3, phospho-mTOR/mTOR, and Beclin 1 were significantly increased after induction of seizures. However, levels of Atg3, Atg14, Atg5-Atg12, Atg7, BAG3, Hsp70, and LAMP1 showed no significant alterations compared to controls. Although KA did not induce neuronal death, this study provides morphological and biochemical evidence that status epilepticus induced by KA activates caspase-3 in mossy fibers and induces autophagy in the C57BL/6 hippocampus. These data indicate that autophagic factors may modulate the sensitivity of pyramidal cells to KA and that autophagy may constitute a part of an endogenous neuroprotective arsenal which might be behind the resistance of C57BL/6-hippocampal cells to KA-induced neuronal death.

Low-cost composites based on porous titania-apatite surfaces for the removal of patent blue V from water: Effect of chemical structure of dye

Hydroxyapatite/titania nanocomposites (TiHAp) were synthesized from a mixture of a titanium alkoxide solution and dissolution products of a Moroccan natural phosphate. The simultaneous gelation and precipitation processes occurring at room temperature led to the formation of TiHAp nanocomposites. X-ray diffraction results indicated that hydroxyapatite and anatase (TiO2) were the major crystalline phases. The specific surface area of the nanocomposites increased with the TiO2 content. Resulting TiHAp powders were assessed for the removal of the patent blue V dye from water. Kinetic experiments suggested that a sequence of adsorption and photodegradation is responsible for discoloration of dye solutions. These results suggest that such hydroxyapatite/titania nanocomposites constitute attractive low-cost materials for the removal of dyes from industrial textile effluent.

Beclin-1 Deficiency Alters Autophagosome Formation, Lysosome Biogenesis and Enhances Neuronal Vulnerability of HT22 Hippocampal Cells

Beclin-1 is assumed to be a critical component participating in autophagosome formation in mammals; however, the exact role of Beclin-1 in autophagy remains controversial. Here (1) we created a HT22-Beclin-1-knockdown cell line using the Q-techBECN1 technique, (2) examined the potential role of Beclin-1 in an autophagic response in hippocampal HT22 neurons challenged with rapamycin, (3) investigated the expression of several gene products involved in the autophagic pathway, and (4) checked the effects of Beclin-1 knockdown on neuronal death induced by AAS. Rapamycin induced and altered the expression of autophagy signature proteins in wild-type cultures as well as in HT22-Beclin-1-knockdown cells. However, among the examined markers, only two factors exhibited dramatic changes when comparing controls to HT22-Beclin-1-knockdown cells. The amount of LC3, an important protein for the initiation of autophagosome formation and LAMP-1, a major constituent of the lysosomal membrane, underwent a dramatic and highly significant increase in control cultures challenged with rapamycin. In contrast, rapamycin was not able to induce any significant changes in LC3 and LAMP-1 levels in HT22-Beclin-1-knockdown cells. In addition, the knockdown of Beclin-1 enhanced neuronal susceptibility to death signals induced by AAS. Our data demonstrate the essential role of Beclin-1 in the formation of autophagosomes and lysosome biogenesis and underline that deletion of this key system is deleterious for cell viability.

Axonal Accumulation of Lysosomal-Associated Membrane Protein 1 (LAMP1) Accompanying Alterations of Autophagy Dynamics in the Rat Hippocampus Upon Seizure-Induced Injury

We found a dramatic upregulation in the expression of LC3 in the hippocampus of rats upon status epilepticus (SE). However, the enhancement in LC3 expression might be caused by a reduction in lysosomal activity or by alterations in autophagosome-lysosome fusion leading to a cytosolic vesicular retention. In order to dissect this aspect, we monitored the spatial and temporal expression of LC3 and LAMP1 in the hippocampus of rats with SE. The Western blot analysis showed that the expression of LAMP1 was slightly increased in hippocampal cells at 6, 24, and 48 h post-SE. However, immunofluorescence analysis showed dramatic spatial changes in LAMP1 distribution within the hippocampus. LAMP1 in controls was localised only in cytosol as dot like staining, however at 24 h post-SE LAMP1 was not only highly expressed, but accumulated in mossy fibers of dentate gyrus. In parallel, we found few scattered LC3-positive-dots in neurites of dentate gyrus which co-localise with LAMP1-positive structures. We conclude that SE not only increased autophagosomal abundance, but also lysosomal activities and a massive accumulation of LAMP1 in axons of dentate gyrus. This could support the hypothesis that the marked increased autophagosomal abundance in cytosol reflects an increase in the autophagic activity more than an inhibition of autophagosomal clearance. Although LAMP1 may have contributed to cell damage in the selective vulnerable hippocampal CA1-subfield, it is also possible that lysosomal/autophagic mechanisms in mossy fibers were compensatory and reflected an attempt to survive the epileptic insult by breaking down non-essential components.

Parameters influencing ciprofloxacin, ofloxacin, amoxicillin and sulfamethoxazole retention by natural and converted calcium phosphates

The retention of four antibiotics, ciprofloxacin, ofloxacin, amoxicillin and sulfamethoxazole by a natural phosphate rock (francolite) was studied and compared with a converted hydroxyapatite powder. The maximum sorption capacities were found to correlate with the molecular weight of the molecules. The mechanisms of sorption depended mostly on the charge of the antibiotic whereas the kinetics of the process was sensitive to their hydrophobic/hydrophilic character. The two materials showed slightly distinct affinities for the various antibiotics but exhibited similar maximum sorption capacities despite different specific surface areas. This was mainly attributed to the more pronounced hydrophobic character of the francolite phase constituting the natural phosphate. These data enlighten that the retention properties of these mineral phases depend on a complex interplay between the inter-molecular and molecule-solid interactions. These findings are relevant to understand better the contribution of calcium phosphates in the fate and retention of antibiotics in soils.

Status epilepticus in the immature rodent brain alters the dynamics of autophagy

There is considerable interest in defining the molecular pathways involved in seizure-induced neuronal death. Necrotic, apoptotic and anti-apoptotic signalling pathways are activated after status epilepticus (SE). Analyses of apoptosis and necrosis have been merely reported, however conditions of autophagic cell death with hallmarks of type 2 programmed cell death-morphology are relatively few. Autophagy is a highly regulated cellular mechanism for the bulk degradation of cytoplasmic contents which is involved in a variety of physiological and pathological conditions associated with neurological diseases. Our goal was to examine whether autophagy is implicated in the cell death machinery after SE. For this purpose, we used lithium-pilocarpine model of SE in 14-day-old rats and examined the dynamics in the expression of autophagic markers in the hippocampus in controls and in animals subjected to SE at 6, 24, and 48h after the insult. Protein levels of central components of the autophagic machinery were dramatically affected by SE with, however, altered dynamics, compared to controls. Levels of LC3, phospho-mTOR/mTOR, BAG3 and Hsp70 were significantly increased, whereas Beclin 1 levels remained unchanged after SE. The dynamics in the expression of Atg3, Atg5, Atg7, Atg14 and LAMP1 were slightly altered. The amount of SQSTM1/p62 underwent a dramatic and highly significant breakdown 48 h after the induction of SE. These results demonstrate for the first time that SE in the immature brain results in significant alterations of autophagy dynamics. There is a growing interest in the role of autophagy in neurodegeneration, and an emerging consensus that autophagy represents a double-edged sword, acting either as a prosurvival mechanism, or as part of a cell death pathway.

Increased neuronal injury in clock gene Per-1 deficient-mice after cerebral ischemia

Transient, severe global ischemia that arises in humans as a consequence of cardiac arrest or cardiac surgery or that is induced experimentally in animals, leads to selective and delayed neuronal death, particularly in the hippocampus. Especially, in this brain structure, clock genes are rhythmically expressed, for instance the inducible and archetypical clock gene is Period1 (Per1). An eventual involvement of its trans-activating protein products in the daytime-dependent severity of ischemia-induced cell damage is not excluded. Probably, neurons may exhibit endogenously a daytimedependent variation in the expression of predictive cell death proteins. We therefore compared the cell death machinery in the hippocampus between Per1(-/-)- and wildtype (WT) mice upon cerebral ischemia. Neuronal death in the hippocampal CA1-subfield, was observed in both types of mice, but the density of damaged cells in Per1(-/-)-mice was increased by more than 23% as compared to wildtype mice. To explore the mechanisms underlying the excessive vulnerability of the hippocampus in Per1(-/-)-mice and to address if hippocampal susceptibility inherits a daytime component, the expression of both, apoptotic and autophagic predictors of cell death was monitored. In Per1(-/-)-mice, the expression of apoptotic/autophagic markers are altered and higher levels of the proapoptotic factors such as cytochrome c and Apaf-1 were observed as compared to WT mice. Moreover, the autophagy marker LC3B was dramatically reduced in Per1(-/-)- mice. Our data suggests that basal activities of apoptosis and autophagy seem to be modulated by PER1, and that the autophagic machinery is probably slowed down when this clock gene is absent. These alterations may be causal for the observed innate vulnerability of Per1(-/-)-mice to cerebral ischemia.

Alleviation of autophagy by knockdown of Beclin-1 enhances susceptibility of hippocampal neurons to proapoptotic signals induced by amino acid starvation

Autophagy has been described as a cellular response to stressful stimuli like starvation. One of its primary functions is to recycle amino acids from degraded proteins for cellular survival under nutrient deprived conditions. Autophagy is characterized by double membrane cytosolic vesicles called autophagosomes and prolonged autophagy is known to result in autophagic (Type II) cell death. Beclin-1 is involved in the regulation of autophagy in mammalian cells. This study examined the potential impact of knockdown of beclin-1 in an autophagic response in HT22 neurons challenged with amino acid starvation (AAS). AAS exposure induced light chain-3 (LC-3)-immunopositive and monodansylcadaverine (MDC) fluorescent dye-labeled autophagosome formation in cell bodies as early as 3 h post-AAS in wild type cells. Elevated levels of the autophagosome-targeting LC3-II were also observed following AAS. In addition, neuronal death induced by AAS in HT22-cells led to a moderate activation of caspase-3, a slight upregulation of AIF and did not alter the HtrA2 levels. Autophagy inhibition by a knockdown of beclin-1 significantly reduced AAS-induced LC3-II increase, reduced accumulation of autophagosomes, and potentiated AAS-mediated neuronal death. Collectively, this study shows that the both apoptotic and autophagic machineries are inducible in cultured hippocampal HT22 neurons subjected to AAS. Our data further show that attenuation of autophagy by a knockdown of beclin-1 enhanced neurons susceptibility to proapoptotic signals induced by AAS and underlines that autophagy is per se a protective than a deleterious mechanism.

Guidelines for the use and interpretation of assays for monitoring autophagy

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.

Activation of sphingosine kinase 2 is an endogenous protective mechanism in cerebral ischemia

The two ubiquitously expressed sphingosine kinases (SphK) 1 and 2 are key regulators of the sphingolipid signaling pathway. Despite the formation of an identical messenger, i.e. sphingosine 1-phosphate (S1P), they exert strikingly different functions. Particularly, SphK2 is necessary for the phosphorylation of the sphingosine analog fingolimod (FTY720), which is protective in rodent stroke models. Using gene deficient mice lacking either SphK1 or SphK2, we investigated the role of the two lipid kinases in experimental stroke. We performed 2h transient middle cerebral artery occlusion (tMCAO) and analyzed lesion size and neurological function after 24h. Treatment groups received 1mg/kg FTY720. Neutrophil infiltration, microglia activation, mRNA and protein expression of SphK1, SphK2 and the S1P(1) receptor after tMCAO were studied. Genetic deletion of SphK2 but not SphK1 increased ischemic lesion size and worsened neurological function after tMCAO. The protective effect of FTY720 was conserved in SphK1(-/-) mice but not in SphK2(-/-) mice. This suggests that SphK2 activity is an important endogenous protective mechanism in cerebral ischemia and corroborates that the protective effect of FTY720 is mediated via phospho-FTY720.

Pyridine and phenol removal using natural and synthetic apatites as low cost sorbents: influence of porosity and surface interactions

A natural phosphate rock and two synthetic mesoporous hydroxyapatites were evaluated for the removal of pyridine and phenol from aqueous solutions. Experiments performed by the batch method showed that the sorption process occurs by a first order reaction for both pyridine and phenol. In contrast, the Freundlich model was able to describe sorption isotherms for phenol but not for pyridine. In parallel, the three apatites exhibit similar pyridine sorption capacities whereas phenol loading was in agreement with their respective specific surface area. This was attributed to the strong interaction arising between pyridine and apatite surface that hinders further inter-particular diffusion. This study suggests that, despite its low specific surface area, natural phosphate rock may be used as an efficient sorbent material for specific organic pollutants, with comparable efficiency and lower processing costs than some activated carbons.

First appraisal of brain pathology owing to A30P mutant alpha-synuclein

Familial Parkinson disease (PD) due to the A30P mutation in the SNCA gene encoding alpha-synuclein is clinically associated with PD symptoms. In this first pathoanatomical study of the brain of an A30P mutation carrier, we observed neuronal loss in the substantia nigra, locus coeruleus, and dorsal motor vagal nucleus, as well as widespread occurrence of alpha-synuclein immunopositive Lewy bodies, Lewy neurites, and glial aggregates. Alpha-synuclein aggregates ultrastructurally resembled Lewy bodies, and biochemical analyses disclosed a significant load of insoluble alpha-synuclein, indicating neuropathological similarities between A30P disease patients and idiopathic PD, with a more severe neuropathology in A30P carriers.

Anatomical brain connectivity and positive symptoms of schizophrenia: a diffusion tensor imaging study

Structural brain changes in schizophrenia are well documented in the neuroimaging literature. The classical morphometric analyses of magnetic resonance imaging (MRI) data have recently been supplemented by diffusion tensor imaging (DTI), which mainly assesses changes in white matter (WM). DTI increasingly provides evidence for abnormal anatomical connectivity in schizophrenia, most often using fractional anisotropy (FA) as an indicator of the integrity of WM tracts. To better understand the clinical significance of such anatomical changes, we studied FA values in a whole-brain analysis comparing paranoid schizophrenic patients with a history of auditory hallucinations and matched healthy controls. The relationship of WM changes to psychopathology was assessed by correlating FA values with PANSS scores (positive symptoms and severity of auditory hallucinations) and with illness duration. Schizophrenic patients showed FA reductions indicating WM integrity disturbance in the prefrontal regions, external capsule, pyramidal tract, occipitofrontal fasciculus, superior and inferior longitudinal fasciculi, and corpus callosum. The arcuate fasciculus was the only tract which showed increased FA values in patients. Increased FA values in this region correlated with increased severity of auditory hallucinations and length of illness. Our results suggest that local changes in anatomical integrity of WM tracts in schizophrenia may be related to patients' clinical presentation.

The immunomodulatory sphingosine 1-phosphate analog FTY720 reduces lesion size and improves neurological outcome in a mouse model of cerebral ischemia

Cerebral ischemia is accompanied by fulminant cellular and humoral inflammatory changes in the brain which contribute to lesion development after stroke. A tight interplay between the brain and the peripheral immune system leads to a biphasic immune response to stroke consisting of an early activation of peripheral immune cells with massive production of proinflammatory cytokines followed by a systemic immunosuppression within days of cerebral ischemia that is characterized by massive immune cell loss in spleen and thymus. Recent work has documented the importance of T lymphocytes in the early exacerbation of ischemic injury. The lipid signaling mediator sphingosine 1-phosphate-derived stable analog FTY720 (fingolimod) acts as an immunosuppressant and induces lymphopenia by preventing the egress of lymphocytes, especially T cells, from lymph nodes. We found that treatment with FTY720 (1mg/kg) reduced lesion size and improved neurological function after experimental stroke in mice, decreased the numbers of infiltrating neutrophils, activated microglia/macrophages in the ischemic lesion and reduced immunohistochemical features of apoptotic cell death in the lesion.

KAAD-cyclopamine augmented TRAIL-mediated apoptosis in malignant glioma cells by modulating the intrinsic and extrinsic apoptotic pathway

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic. The main obstacle in TRAIL-based therapy is that many glioma cells are resistant. In this study glioblastoma cell lines, human glioblastoma short-term cultures and human astrocytes were treated with 3-keto-N-aminoethylaminoethylcaproyldihydrocinnamoyl cyclopamine (KAAD-cyclopamine), tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) or the combination of both. Single treatment with KAAD-cyclopamine or TRAIL does not induce cytotoxicity in malignant glioma cells. However, treatment with KAAD-cyclopamine in combination with TRAIL induces rapid apoptosis in TRAIL-resistant glioma cells. Notably, normal human astrocytes were not affected by the combination treatment consisting of KAAD-cyclopamine and TRAIL. KAAD-cyclopamine led to an upregulation of death receptor 4 and 5 and down-regulation of bcl-2 and c-FLIP. Furthermore, overexpression of both bcl-2 and c-FLIP attenuated KAAD-cyclopamine facilitated TRAIL-mediated apoptosis. Taken together,we provided evidence that KAAD-cyclopamine facilitated TRAIL-mediated apoptosis at the level of the intrinsic and extrinsic apoptotic pathways in malignant glioma cells.

Quercetin promotes degradation of survivin and thereby enhances death-receptor-mediated apoptosis in glioma cells

The flavonoid quercetin has been reported to inhibit the proliferation of cancer cells, whereas it has no effect on nonneoplastic cells. U87-MG, U251, A172, LN229, and U373 malignant glioma cells were treated with quercetin (50-200 microM). Quercetin did not cause cytotoxicity 24 h after treatment. Combining quercetin with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) strongly augmented TRAIL-mediated apoptosis in U87-MG, U251, A172, and LN229 glioma cells; U373 cells could not be sensitized by quercetin to TRAIL-mediated apoptosis. TRAIL-induced apoptosis was enhanced by quercetin-induced reduction of survivin protein levels. Upon treatment with quercetin, the protein level of survivin was strongly suppressed in U87-MG, U251, and A172 but not in U373 glioma cells. Quercetin exposure resulted in proteasomal degradation of survivin. TRAIL-quercetin-induced apoptosis was markedly reduced by overexpression of survivin. In addition, upon treatment with quercetin, downregulation of survivin was also regulated by the Akt pathway. Taken together, the results of the present study suggest that quercetin sensitizes glioma cells to death-receptor-mediated apoptosis by suppression of inhibitor of the apoptosis protein survivin.

TRAIL-mediated apoptosis in malignant glioma cells is augmented by celecoxib through proteasomal degradation of survivin

Celecoxib is a cyclooxygenase 2-selective nonsteroidal anti-inflammatory drug (NSAID) that exhibited therapeutic activity in cancer. In this study three malignant glioma, U87-MG, U251 and A172, were treated with celecoxib, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or the combination of both. Single treatment with celecoxib (25-100muM) for 24h resulted in a concentration-dependant decrease of cellular viability in U87-MG, U251 and A172. Combining subtoxic concentrations of celecoxib with TRAIL strongly increased cell death in human malignant glioma cells. After 8h treatment with celecoxib we found down-regulation of the inhibitor of apoptosis protein survivin that was mediated by proteasomal degradation. In addition, over-expression of survivin not only attenuated celecoxib-induced cytotoxicity but also cytotoxicity induced by the combination of celecoxib and TRAIL. Taken together, in malignant glioma survivin is a key regulator in celecoxib- and TRAIL-celecoxib-mediated cell death.

Apoptosis meets autophagy-like cell death in the ischemic penumbra: Two sides of the same coin?

Autophagy is a homeostatic cellular process required for the recycling of proteins and damaged organelles, and in most scenarios is believed to promote cell survival. However, there is accumulating evidence that under certain pathological situations, autophagy can also trigger and mediate programmed cell death (type II death). Despite the well-established pathophysiological role of apoptosis (type I cell death) in post-ischemic neuron death, there is now increasing interest whether alternative types of programmed cell death might be involved in regulation of neuronal death after both global and focal cerebral ischemia. Initial studies demonstrating the involvement of lysosomal proteases of the cathepsin family in neuron death after global ischemia already had suggested that this type of cell death may occur in an autophagy-dependent manner. Recently it was also shown that focal ischemia is associated with potently enhanced expression of the autophagy regulator Beclin 1 and subcellular redistribution of the autophagic marker LC3 to vacuolic structures in ischemic neurons. Increasing evidence suggests that the effects of autophagy are highly contextual. An insufficient autophagic response might render cells more susceptible to stress conditions whereas on the other hand prolonged overactivation of autophagy can lead to a complete self digestion of the cell. The extent of autophagy may represent a master switch between cell survival and cell death, and it will be of fundamental importance to dissect whether autophagy is primarily a strategy for survival or whether autophagy can also be a part of a cell death program and thus contribute to cell death after cerebral ischemia. A profound understanding of the biological effects and the mechanisms underlying ischemia-induced autophagy in neurons might be helpful in seeking effective new treatments for cerebral ischemia.

Guidelines for the use and interpretation of assays for monitoring autophagy in higher eukaryotes

Research in autophagy continues to accelerate,(1) and as a result many new scientists are entering the field. Accordingly, it is important to establish a standard set of criteria for monitoring macroautophagy in different organisms. Recent reviews have described the range of assays that have been used for this purpose.(2,3) There are many useful and convenient methods that can be used to monitor macroautophagy in yeast, but relatively few in other model systems, and there is much confusion regarding acceptable methods to measure macroautophagy in higher eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers of autophagosomes versus those that measure flux through the autophagy pathway; thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from fully functional autophagy that includes delivery to, and degradation within, lysosomes (in most higher eukaryotes) or the vacuole (in plants and fungi). Here, we present a set of guidelines for the selection and interpretation of the methods that can be used by investigators who are attempting to examine macroautophagy and related processes, as well as by reviewers who need to provide realistic and reasonable critiques of papers that investigate these processes. This set of guidelines is not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to verify an autophagic response.

Upregulation of Beclin 1 in the ischemic penumbra

Here we discuss the probable role of autophagy in cerebral ischemia based on our own recent data and the literature. We examined the protein level of Beclin 1 (Bcl-2 interacting protein) and microtubule-associated protein 1 light chain 3 (LC3) which were previously found to promote autophagy. We found a dramatic elevation in Beclin 1 levels and LC3 in the penumbra of rats challenged by cerebral ischemia. We found also that a subpopulation of Beclin 1-upregulating cells is also expressing the active form of caspase-3, and that all Beclin 1 upregulating cells display dense staining of LC3. Neuronal cells that overexpress Beclin 1 may exhibit damaged DNA but without changes in nuclear morphology, which indicates that not all the Beclin 1-upregulating cells are predestined to die. We conclude that the cell death in the penumbra bears a resemblance not only to necrosis, apoptosis, or a compromise between the two, but exhibits also biochemical and morphological characteristics of autophagic cell death. The question that constantly arises, however, is whether autophagic activity in damaged cells is the cause of death or is actually an attempt to prevent it as a part of an endogenous neuroprotective response.

Synergetic effects of caspase 3 and mu-calpain in XIAP-breakdown upon focal cerebral ischemia

Dysregulation of apoptosis is involved in a wide spectrum of disease ranging from proliferative to neurodegenerative disorders. The recently discovered X-linked inhibitor of apoptosis protein (XIAP) is among the most potent inhibitors of apoptosis. This protein binds to and inhibits both initiator caspases and effector caspases such as caspase-3. The aim of this study was to investigate the relationships between XIAP-breakdown, caspase activation in the development of delayed infarct upon ischemia. We demonstrated that endogenous XIAP is cleaved at least into two fragments during reperfusion following the ischemic insult. The two fragments produced seem to be related to caspase-3 and mu-calpain activities, which are massively enhanced in tissues challenged by ischemia. Therefore, degradation of XIAP by mu-calpain in our system may decrease the activation threshold of caspase-3 normally held in check by the IAPs and/or lead to auto-activation of other caspases.

The serine protease Omi/HtrA2 is involved in XIAP cleavage and in neuronal cell death following focal cerebral ischemia/reperfusion

Omi/HtrA2 is a pro-apoptotic mitochondrial serine protease involved in both forms of apoptosis, caspase-dependent as well as caspase-independent cell death. However, the impact of Omi/HtrA2 in the apoptotic cell machinery that takes place in vivo under pathological conditions such as cerebral ischemia remains unknown. The present study was monitored in order to examine whether Omi/HtrA2 plays a decisive role in apoptosis observed after focal cerebral ischemia in rats. Male adult rats were subjected to 90min of focal cerebral ischemia followed by reperfusion and treated with vehicle or ucf-101, a novel and specific Omi/HtrA2 inhibitor, prior reperfusion. Focal cerebral ischemia/reperfusion induced a mitochondrial up-regulation of Omi/HtrA2 and significantly increased cytosolic accumulation of Omi/HtrA2. Furthermore, ischemia led to activation of caspase-3 and degradation X-linked inhibitor of apoptosis protein (XIAP). Treatment of animals prior ischemia with ucf-101, the specific inhibitor of Omi/HtrA2, was able to (1) reduce the number of TUNEL-positive cells, to (2) attenuate the XIAP-breakdown and to (3) reduce the infarct size. This study shows for the first time that focal cerebral ischemia in rats results in Omi/HtrA2 translocation from the mitochondria to the cytosol, where it participates in neuronal cell death. Blocking the proteolytic activity of Omi/HtrA2 with specific inhibitors, such as the ucf-101, could be a novel way to afford neuroprotection and minimize cellular damage in cerebral ischemia/reperfusion.

Expression of the gene encoding the pro-apoptotic BNIP3 protein and stimulation of hypoxia-inducible factor-1α (HIF-1α) protein following focal cerebral ischemia in rats

Hypoxia is a common cause of cell death and is implicated in many disease processes including stroke and chronic degenerative disorders. In response to hypoxia, cells express a variety of genes which allow adaptation to altered metabolic demands, decreased oxygen demands, and the removal of irreversibly damaged cells. Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that regulates the adaptive response to hypoxia in cells. In this study, we reported an early, time-related, gradual up-regulation of HIF-1alpha, and a moderate increase in vascular endothelial growth factor (VEGF)- and erythropoietin (Epo)-levels following transient focal ischemia. Moreover, we demonstrated, for the first time a specific localization of the pro-apoptotic regulator BNIP3 in striatal and cortical neurons after transient focal ischemia in rats. Prolonged intranuclear BNIP3 immunoreactivity was associated with delayed neuronal death. Experiments showed protein increases on Western blots of brain tissue with peaks at 48h after ischemia. Epo responds to ischemia in an early stage, whereas VEGF and BNIP3 accumulate in cells at later times after ischemia. This suggests the possibility that BH3-only proteins might be one of the major downstream effectors of HIF-1alpha in hypoxic cell death. These findings open the possibility that the hypoxia-regulated pro-apoptotic protein BNIP3 enters the nucleus and could interact with other proteins involved in DNA structure, transcription or mRNA splicing after focal brain ischemia.

Control of fetal growth and neonatal survival by the RasGAP-associated endoribonuclease G3BP

The regulation of mRNA stability plays a major role in the control of gene expression during cell proliferation, differentiation, and development. Here, we show that inactivation of the RasGAP-associated endoribonuclease (G3BP)-encoding gene leads to embryonic lethality and growth retardation. G3BP-/- mice that survived to term exhibited increased apoptotic cell death in the central nervous system and neonatal lethality. Both in mouse embryonic fibroblasts and during development, the absence of G3BP altered the expression of essential growth factors, among which imprinted gene products and growth arrest-specific mRNAs were outstanding. The results demonstrate that G3BP is essential for proper embryonic growth and development by mediating the coordinate expression of multiple imprinted growth-regulatory transcripts.