抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

/pdf/nitric-oxide-and-peroxynitrite-in-health-and-disease-3uuuqgfdcz.pdf

Nitric Oxide and Peroxynitrite in Health and Disease

Autophagy is a process by which components of the cell are degraded to maintain essential activity and viability in response to nutrient limitation. Extensive genetic studies have shown that the yeast ATG1 kinase has an essential role in autophagy induction. Furthermore, autophagy is promoted by AMP activated protein kinase (AMPK), which is a key energy sensor and regulates cellular metabolism to maintain energy homeostasis. Conversely, autophagy is inhibited by the mammalian target of rapamycin (mTOR), a central cell-growth regulator that integrates growth factor and nutrient signals. Here we demonstrate a molecular mechanism for regulation of the mammalian autophagy-initiating kinase Ulk1, a homologue of yeast ATG1. Under glucose starvation, AMPK promotes autophagy by directly activating Ulk1 through phosphorylation of Ser 317 and Ser 777. Under nutrient sufficiency, high mTOR activity prevents Ulk1 activation by phosphorylating Ulk1 Ser 757 and disrupting the interaction between Ulk1 and AMPK. This coordinated phosphorylation is important for Ulk1 in autophagy induction. Our study has revealed a signalling mechanism for Ulk1 regulation and autophagy induction in response to nutrient signalling.

/pdf/ampk-and-mtor-regulate-autophagy-through-direct-14wqsz16ke.pdf

AMPK and mTOR regulate autophagy through direct phosphorylation of Ulk1

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.

For example, 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 versus those that measure flux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase 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. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy.

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. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation, it is imperative to target by gene knockout or RNA interference more than one autophagy-related protein. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways implying that not all Atg proteins can be used as a specific marker for an autophagic process. 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 assays, we hope to encourage technical innovation in the field.

/pdf/guidelines-for-the-use-and-interpretation-of-assays-for-ijf2t30pbq.pdf

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

Alzheimer’s disease (AD), the most common form of dementia, affects 55 million people worldwide, and this number is expected to increase to 88 million by 2050. Understanding the molecular mechanisms underpinning pathological cognitive deficits and AD onset and progression is urgently needed, to identify biomarkers and therapeutic targets. Besides ageing, type 2 diabetes (T2D) and obesity are considered major risk factors for cognitive decline and AD. Here, we discuss the mechanistic relationship between AD and metabolic disorders, particularly T2D and obesity. The repurposing of anti-diabetes and anti-obesity approaches in the treatment of AD will be also debated.

Cognitive Impairment in Obesity and Diabetes

The case for exercise in brain health is continuing to deepen to the point where it seems the weight room is as critical for brain function as it is for building muscle mass. Increased cardiovascular function, improved psychological profile, increased neurotrophic factors and neurogenesis are but a few of the factors linked to the benefits of vigorous exercise. A mechanistic understanding of how exercise can bring about such a pleotrophic range of changes has remained elusive prior to the study by Swerdlow and colleagues published in this issue of Journal of Neurochemistry (Lezi et al. 2013). Insightfully, these investigators used the most elementary product of exercise physiology, lactate, to mimic exercise. The authors found that lactate administered to resting mice produced many of the same benefits to brain mitochondria density found during extensive exercise. This elegant and simple approach opens exercise benefits to pharmacological intervention, possibly with lactate analogues if not lactate itself. It also offers the hope that exercise mimetics can help those who cannot sustain vigorous exercise. Even more significantly, the findings link exercise to the observed benefits of pre-conditioning treatments. High lactate levels are usually considered a negative metabolic modulator, yet in Swerdlow’s study the result indicates an increase in metabolic capacity. This apparent paradox, pre-conditioning, is a phenomenon whereby a sub-lethal condition protects against a subsequent potential lethal condition by stimulating endogenous adaptive and pro-survival events. As a matter of fact, hypoxia, as well as mitochondrial modulators such as cyanide, was shown to protect brain endothelial and neuronal cells against diabetes-mediated deleterious effects and other injurious conditions (Correia et al., 2011, 2012). However, an intriguing question can arise: what is the common denominator that explains the similar brain protective effects exerted by extensive exercise, exogenous lactate administration, and the preconditioning phenomenon? Despite the fact that at the end of animal treatments no significant alterations in hypoxia-inducible factor-1α (HIF-1α) mRNA and protein levels were observed, we strongly believe that this transcription factor may trigger the initial protective response mediated by extensive exercise and exogenous lactate administration. And why HIF-1α? First and foremost, the abovementioned conditions (exercise, lactate and preconditioning) per se are able to activate HIF-1α (Ameln et al. 2005, O’Hagan et al. 2009, De Saedeleer et al. 2012, Correia et al. 2011). Secondly, the metabolic switch from mitochondrial respiration towards glycolysis, in order to favor lactate production, is driven by HIF-1α. Third, recent advances in HIF-1α biology have revealed that the function of this fascinating transcription factor in the brain is not restricted to the regulation of energy metabolism; it also plays a role in the orchestration of several vital processes for normal brain functioning, including erythropoiesis, angiogenesis and neurogenesis. Lastly, HIF-1α is a major piece that integrates the mitochondrial puzzle, being involved in the coordination of many aspects of mitochondrial life cycle and transport. For instance, HIF-1α regulates mitochondrial fusion-fission events, autophagy, and mitochondrial transport and distribution in neurons by favoring the mitochondrial trafficking in the anterograde direction. Interestingly, HIF-1α also facilitates mitochondrial biogenesis (Correia et al. 2011, 2013). Within this scenario, further studies focusing on the dynamic behavior of HIF-1α gene expression during extensive exercise and lactate treatment as well as the genetic manipulation of HIF-1α expression are required to help shed light on the mechanistic basis underlying the brain protective effects shared by exercise and exogenous lactate administration.

Is exercise-in-a-bottle likely to proffer new insights into Alzheimer's disease?

Oxidative Stress and Balance in Neurodegenerative Diseases

β-amyloid peptide (Aβ) accumulation is the hallmark of Alzheimer9s Disease (AD), but the mechanisms underlying its cellular toxicity are unclear. Evidence shows a close association between Type 2 diabetes (DM) and AD. DM also promotes impaired function of cerebrovascular endothelium that constitutes the blood-brain barrier. We hypothesized that hyperglycemia-induced mitochondrial dysfunction and oxidative stress promote Aβ toxicity in endothelial cells. Methods. Rat brain microvascular endothelial cells (RBMEC) were isolated from adult Sprague-Dawley rats and cultured in normoglycemic and hyperglycemic media followed by exposure to Aβ peptide or Aβ 40-1. Cell viability was measured by the Alamar blue assay and mitochondrial membrane potential (Ψ mito ) was measured by confocal microscopy and microplate reader (rhodamine 123). Also, mitochondrial superoxide (mitoSO) was measured by fluorescence microscopy (MitoSOX) and Hydrogen peroxide (H 2 O 2 ) levels by microplate reader (Amplex Red). RBMECs were treated with antioxidants (MitoTempo and PEG-SOD) to study the role of oxidative stress in Aβ-toxicity. Results. Hyperglycemia, mannitol, Aβ or Aβ 40-1 alone did not affect cell viability. However, during hyperglycemia, Aβ reduced the cell viability compared to normoglycemic conditions. Baseline Ψ mito and depolarization in response to ionophore were not different among all treatment groups. Aβ and hyperglycemia together induced a reduction in Ψ mito , promoted mitochondrial fission and enhanced mitoSO production and H 2 O 2 levels. Only MitoTempo and PEG-SOD treatments were able to counteract Aβ toxicity by increasing cell viability and recovering Ψ mito response. Conclusion. Hyperglycemia increases RBMEC susceptibility to Aβ toxicity leading to cell death by promoting the alterations of mitochondrial morphology, electromotive force and enhanced oxidative stress. The effect of hyperglycemia to promote Aβ toxicity appears to be mediated by mitoSO.

Abstract 17944: Increased Susceptibility to β-amyloid Toxicity In Rat Brain Microvascular Endothelial Cells Under Hyperglycemic Conditions

Hydroxynonenal-Generated Crosslinking Fluorophore and Mitochondria-derived Lipoic Acid Accumulation in Alzheimer Disease Reveal a Dichotomy of Protein Turnover

Paula I. Moreira

Papers

Cognitive Impairment in Obesity and Diabetes

Is exercise-in-a-bottle likely to proffer new insights into Alzheimer's disease?

Oxidative Stress and Balance in Neurodegenerative Diseases

Abstract 17944: Increased Susceptibility to β-amyloid Toxicity In Rat Brain Microvascular Endothelial Cells Under Hyperglycemic Conditions

Hydroxynonenal-Generated Crosslinking Fluorophore and Mitochondria-derived Lipoic Acid Accumulation in Alzheimer Disease Reveal a Dichotomy of Protein Turnover